Pyoderma Gangrenosum: Diagnosis and Treatment of a Rare Skin Disorder
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
Pyoderma gangrenosum (PG) is a rare inflammatory skin disorder characterized by the
development of painful ulcerating lesions that can increase rapidly in size. While the exact
cause of PG is still unknown, it is considered an auto-inflammatory condition associated with
systemic diseases such as ulcerative colitis, arthritis, and hematologic malignancies in up to
50% of cases. Due to its rarity and variable clinical presentation, PG remains a clinical
challenge to diagnose and treat effectively. This paper will discuss the pathogenesis, clinical
manifestations, diagnostic evaluation, and current therapeutic approaches for pyoderma
gangrenosum.
Pathogenesis
The precise pathogenesis of PG remains unclear. However, it is generally accepted to be an
auto-inflammatory condition rather than an infective or autoimmune disease. Significant
advances have been made in understanding the role of aberrant immune responses and
inflammatory pathways that likely contribute to lesion development and progression in PG.
One of the leading theories suggests that PG occurs due to an abnormal neutrophilic driven
response against dermal components. Neutrophils are the predominant inflammatory cells
found within PG lesions and laboratory studies demonstrate increased neutrophil recruitment,
activation, and impairment of apoptosis that prolongs their inflammatory role. Increased
levels of pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, IL-8, IL-17 and
TNF-α have been found both locally within lesions as well as systemically in PG patients.
These mediators are believed to stimulate neutrophil accumulation and activation leading to
proteolytic and oxidative damage of dermal structures.
Genetic factors may also play a role, as PG has been associated with mutations in genes
regulating neutrophil function and recruitment such as CXCR2 and PTPN6. Dysregulation of
matrix metalloproteinases (MMPs) that degrade extracellular matrix components also appears
significant in PG lesion pathogenesis. Higher levels of MMP-1, MMP-8 and MMP-9 have
been detected both locally and systemically compared to healthy controls. Excessive
proteolytic activity from neutrophils and MMPs likely contributes to ulceration of skin and
subcutaneous tissues seen in established PG lesions.
Apart from neutrophils, other inflammatory cells such as mast cells, eosinophils, lymphocytes
and macrophages have been implicated in PG. Elevated tumor necrosis factor alpha (TNF-α)
and interleukin 1 beta (IL-1β) found in PG lesions suggest an activated keratinocyte
phenotype contributing to the inflammatory response as well. Pathogenic bacterial or viral
infections do not appear to directly incite or perpetuate PG lesions, although secondary
infection is common particularly with ulcerated lesions. In summary, multiple inflammatory
pathways dysregulated involving innate and adaptive immune cells contribute to the complex
pathogenesis of PG.
Clinical Manifestations
Pyoderma gangrenosum typically presents as one or more painful papules, pustules, nodules
or vesicles on the skin that rapidly progress to form ulcerations with irregular, violaceous,
undermined borders. These ulcers can vary substantially in size from small <1cm to large
>10cm. Common sites of involvement include the lower legs, but virtually any cutaneous
surface can be affected including the upper extremities, face, genitalia and mucous
membranes. Oral pyoderma gangrenosum accounts for up to 10% of cases. Lesions tend not
to cross the midline.
The clinical course of PG is variable marked by periods of spontaneous lesion exacerbation
followed by unpredictable resolution. In some cases, PG lesions appear suddenly without
precursor papules or vesicles. These are described as pathergic which means incited or
exacerbated by trauma including minor abrasions, surgery, venipuncture, injections or
medical devices applied to the skin. Pathergy is reported in up to 30-50% of PG cases and
emphasizes its proclivity for traumatic inoculation. Pyoderma gangrenosum pustulosum
represents a unique variant characterized by sterile pustules on an erythematous base that
enlarge to form multiple small ulcers scattered over the affected area, most often the lower
legs.
Systemic manifestations of PG typically coincide or follow cutaneous involvement and help
direct further evaluation. Mucous membrane PG should raise concern for underlying
inflammatory bowel disease in up to 50% of patients which is most often ulcerative colitis.
Joint manifestations ranging from arthralgia to seronegative inflammatory arthritis occur in
20-30% of PG patients and raise suspicion for spondyloarthropathies or rheumatological
conditions. Ocular involvement in the form of conjunctivitis, episcleritis or uveitis occurs less
frequently. Hematological malignancies are seen in 3-10% of cases usually preceding PG
onset, so screening tests may be indicated. Constitutional symptoms including fatigue,
weakness, fever and weight loss may accompany severe or recalcitrant PG. Laboratory
abnormalities are generally non-specific showing evidence of an acute phase response with
elevated ESR and CRP levels.
Diagnosis
The clinical diagnosis of PG remains a challenge due to its rarity, heterogeneous presentation
and ability to mimic other conditions. The diagnostic criteria established by Suzuki and
colleagues in 2013 are most commonly used and require at least one major criteria and two
minor criteria for diagnosis.
Major criteria:
- Ulcerative lesion(s) with violaceous margins developing rapidly (within days) at site
exposed to minor trauma
Minor criteria:
- Histopathology showing neutrophilic infiltrate without evidence of infection or vasculitis
- Refractory to standard wound treatment within 3 weeks
- Association with inflammatory bowel disease (IBD), arthritis or other auto inflammatory
conditions
- Resolution of lesions with systemic immunosuppressive therapy
- Pathergy phenomenon (aggravation of lesions from minor trauma or surgery)
A biopsy for histopathology should always be obtained from an active ulcer edge to evaluate
for neutrophilic infiltration, absence of significant vasculitis and rule out infection. Given its
non-specific presentation and overlap with other ulcerative conditions, the differential
diagnosis for PG is extensive and includes infections, vasculitides, factitial dermatitis,
vascular insufficiency ulcers, erythema induratum and malignancy. A thorough history,
physical exam and diagnostic workup is required to confirm the diagnosis and guide
appropriate management. This includes screening assessments for associated systemic
diseases, complete blood count, inflammatory markers, autoimmune serologies, wound
cultures and imaging as clinically indicated. The diagnosis rests on a combination of
characteristic clinical features, compatible histology and exclusion of alternative diagnoses
based on thorough evaluation.
Treatment Approaches
The treatment of PG remains challenging given our incomplete understanding of its
pathophysiology and variable disease course. Therapy is aimed at controlling inflammation,
resolving lesions and preventing recurrences utilizing a combination of topical, intralesional,
systemic and surgical approaches tailored based on disease severity and patient factors.
Topical therapy: Topical corticosteroids, tacrolimus ointment and psoralen with ultraviolet A
(PUVA) phototherapy may benefit less severe, localized PG without ulceration. These
options help reduce surrounding inflammation but cannot induce healing of established
ulcers. Occlusive dressings combined with topical treatment forms the mainstay for
secondary prevention of infection at wound sites.
Intralesional therapy: Steroids have been injected directly into ulcer beds and wound borders
to modulate the inflammatory response with variable success. Alternatives include tacrolimus
and recombinant growth factors to promote wound healing. Repeated applications are often
necessary.
Systemic therapy: Oral corticosteroids are frequently initiated to control acute PG flares,
usually starting at 30-60mg of prednisone daily then tapering over weeks to months. Their
long-term use is limited due to significant adverse effects. In refractory or severe cases,
immunosuppressants serve as steroid-sparing agents. Common options include azathioprine,
cyclosporine, methotrexate, mycophenolate mofetil and tacrolimus among others. These aim
to impede abnormal neutrophil recruitment and function through various mechanisms.
Biologics targeting TNF-α with infliximab or adalimumab provide an effective alternative
especially in PG associated with IBD or arthritis. Newer immunomodulators like tofacitinib
inhibiting Janus kinases are emerging therapies as well. Intravenous immunoglobulin (IVIG)
may benefit patients intolerant of or refractory to conventional immunosuppressants.
Surgical therapy: Debridement, skin grafting or rotational flaps aid wound closure in
refractory ulcers exceeding 6 months duration despite optimal medical management. Simple
compression dressings can help limb dependent ulcers heal. Minor autologous skin grafting
also serves an adjuvant role by reducing inflammation and inducing a proliferative wound
environment. Large ulcerous defects necessitate split or full thickness skin grafts often
requiring tissue expansion or free flaps to obtain closure. The surgical goals are limiting
tissue damage, reducing pathergy risk and preventing contractures-all facilitating optimal
medical treatment.
Adjuvant/supportive measures: Nutritional support, venous insufficiency screening and
compression stockings help address potential exacerbating factors and optimize wound
healing. Pain control, topical antibiotics for secondary infection, pressure offloading and
immobilization for pathergy prone regions complement medical and surgical therapy.
Psychological evaluation and support aids coping especially with disfiguring recalcitrant
disease or associated conditions like IBD. Multidisciplinary input from dermatologists,
rheumatologists, surgeons and IBD specialists streamlines complex management and follow
up care over time.
Prognosis
With optimal treatment selection and adherence, the prognosis of pyoderma gangrenosum is
generally good. Up to 70-80% of patients achieve complete remission when treated
aggressively based on severity and associated systemic conditions. Factors portending a
worse outcome include extensive or mutilating cutaneous involvement, pathergy, association
with inflammatory bowel disease, hematological or visceral malignancies and lack of
response to conventional therapy. Additionally, PG can have a relapsing course in up to 50%
of patients over time requiring long-term follow up and management strategies. Despite
therapeutic advances, recalcitrant forms of PG resistant to multiple immunosuppressants
carry significant morbidity due to persistent ulcers, scarring, contractures, functional deficits
and quality of life issues. Mortality directly attributed to PG is rare currently estimated at less
than 5% resulting from severe sepsis, visceral crises or hematological malignancies in select
settings. With a multidisciplinary treatment approach and continued research, prognosis
continues to steadily improve for most individuals affected by this challenging neutrophilic
dermatosis.
Conclusion
In summary, pyoderma gangrenosum remains an enigmatic ulcerative skin condition with
pathogenic involvement of multiple inflammatory pathways. While its exact etiology remains
elusive, significant strides have been made in our understanding of PG's complex interplay
between aberrant immune responses, neutrophil dysfunction and protease mediated
extracellular matrix damage causing its characteristic ulcer development. PG poses a
diagnostic challenge due to variable clinical presentation and overlap with other entities.
Thorough clinical evaluation including histopathology and appropriate screening assessments
guide accurate diagnosis and search for potential associated inflammatory, visceral or
hematological disorders. Treatment selection necessitates consideration of disease severity,
extent and any comorbid conditions. Early aggressive multi-modal medical approaches in
combination with supportive measures can induce remission in many cases. With ongoing
immunological and genetic research, new therapeutic targets may arise eventually leading to
more specific, efficacious and safer treatment options for pyoderma gangrenosum. Its
prognosis overall is favorable for most, but complexity dictates ongoing multidisciplinary
care and long term follow up.
