12.Wk4Soap

       

                       

                             

                               

                                   

                             

                                   

                                 

                         

                               

                             

                               

                             

                                   

                     

                                   

                           

                                 

 

                               

                                   

             

         

                   

                             

 

                         

     

       

         

                               

C H A P T E R 2 8

Rashes and skin lesions

Dermatologic problems result from a number of mechanisms, including inflammatory, infectious, immunologic, and environmental (traumatic and exposure induced). At times, the mechanism may be readily identified, such as the infectious bacterial etiology in impetigo. However, some dermatologic lesions may be classified in more than one way. Most insect bites, for example, involve both environmental (the bite) and inflammatory (the response) mechanisms. Awareness of the potential mechanism of any skin disorder is most helpful in identifying the risk a person may have for other illnesses. For example, people with eczema are also frequently at risk for other atopic conditions, notably asthma and allergic rhinitis. Thousands of skin disorders have been described, but only a small number account for the majority of patient visits. Evaluation of rashes and skin lesions depends on a carefully focused history and physical examination. The

provider needs to be familiar with the characteristics of various skin lesions; anatomy, physiology, and pathophysiology of the skin; clinical appearance of the basic lesion; arrangement and distribution of the lesion; and associated pathological conditions. It is also important to know common symptoms associated with specific lesions such as itching or fever. It is necessary to quickly identify life-threatening diseases and those that are highly contagious. Ultimately, competence in dermatologic assessment involves recognition through repetition.

Diagnostic reasoning: Initial focused physical examination

Initial inspection Dermatologic assessment is similar to the assessment of most other body systems in that it depends on patient history and physical assessment. However, sometimes a brief physical assessment preceding the history can assist in the development of the initial differential diagnoses followed by a focused history and further physical examination.

Morphologic criteria Examination involves the classification of the lesion based on a number of morphologic features (examples are listed in Tables 28.1 and 28.2 and illustrated in Figs. 28.1 and 28.2). Evaluation should be systematic. Generally, morphologic features should be analyzed as follows:

• Identify the location of the lesion(s). • Identify the distribution of the lesions as localized, regional, or generalized. • Identify whether the lesion is primary (appearing initially) or secondary (resulting from a change in a primary lesion).

• Identify the shape of the lesion and any arrangement if numerous lesions are present. • Assess the margins (borders). • Assess the pigmentation, including variations. • Palpate to assess texture and consistency. • Measure the size of an individual lesion or estimate the size if lesions are numerous or widespread.

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FIGURE 28.1 Types of skin lesions. Source: (From, Ball JW, Dains JE, Flynn J, et al: Seidel’s guide to physical examination, ed. 8, St. Louis, 2015, Elsevier.)

FIGURE 28.2 Typical distribution of papulosquamous eruptions in children. A, Atopic dermatitis: usually located on the cheeks, creases of elbows, and knees. B, Seborrheic dermatitis: usually located on the scalp, behind the ears, in thigh creases, and in eyebrows. C, Scabies: usually located on the axillae, webs of fingers and toes, and intragluteal area. Source: (From Berkowitz C: Pediatrics: A primary care approach, ed. 2, Philadelphia, 2000, Saunders.)

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Table 28.1

Morphologic Criteria of Rashes and Skin Lesions

PRIMARY LESIONS (DEVELOP INITIALLY IN RESPONSE TO CHANGE IN INTERNAL OR EXTERNAL ENVIRONMENT OF SKIN)

Macule Discrete flat change in color of skin; usually <1.5-cm diameter

Freckle, lentigo, purpura

Patch Discrete flat lesion (large macule); usually >1.5-cm diameter

Pityriasis rosea, melasma, lentigo

Papule Discrete palpable elevation of skin; <1-cm diameter; origin may be epidermal, dermal, or both

Nevi, seborrheic keratosis, dermatofibroma

Nodule Discrete palpable elevation of skin; may evolve from papule; may involve any level of skin from epidermis to subcutis

Nevi, basal cell carcinoma, keratoacanthoma

Plaque Slightly raised lesion, typically with flat surface; >1-cm diameter; scaling frequently present

Psoriasis, mycosis fungoides

Urticaria

NATURE OF DESCRIPTION EXAMPLES

LESION

Wheal Transient pink/red swelling of skin; often displaying central clearing; various shapes and sizes; usually pruritic and lasts <24 hr

Tumor Large papule or nodule; usually >1-cm diameter

Pustule Raised lesion <0.5-cm diameter containing yellow cloudy fluid (usually infected)

Vesicle Raised lesion <0.5-cm diameter containing clear fluid

Bulla Vesicle >0.5-cm diameter

Cyst Semisolid lesion; varies in size from several mm to several cm; may become infected

Basal cell carcinoma, squamous cell carcinoma, malignant melanoma

Folliculitis, acne (closed comedones)

Herpes simplex, herpes zoster, contact (irritant) dermatitis

Bullous pemphigoid, contact (irritant) dermatitis, blisters of second- degree sunburn

Sebaceous cyst

SECONDARY LESIONS (APPEAR AS RESULT OF CHANGES IN PRIMARY LESIONS)

Crust

Scale

Excoriation

Dried exudate that may have been serous, purulent, or hemorrhagic

Thin plates of desquamated stratum corneum that flake off rather easily

Shallow hemorrhagic excavation; linear or punctate; results from scratching

Lichenification Thickening of skin with exaggeration of skin creases; hallmark of chronic eczematous dermatitis

Erosion Partial break in epidermis

Impetigo, herpes zoster (late phase)

Xerosis, ichthyosis, psoriasis

Contact (irritant) dermatitis

Chronic eczema

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NATURE OF DESCRIPTION EXAMPLES

LESION

Herpes simplex or zoster, pemphigus vulgaris

Fissure Linear crack in epidermis Xerosis, angular cheilitis, severe eczema

DISTRIBUTION OF LESIONS

Localized Lesion appears in one small area Impetigo, herpes simplex (e.g., labialis), tinea corporis (“ringworm”)

Regional Lesions involve specific region of body Acne vulgaris (pilosebaceous gland distribution), psoriasis (extensor surfaces and skinfolds)

Generalized Lesions appear widely distributed or in numerous areas simultaneously

Urticaria, disseminated drug eruptions

SHAPE AND ARRANGEMENT

Round or discoid Coin or ring shaped (no central clearing) Nummular eczema

Oval Ovoid shape Pityriasis rosea

Annular Round, active margins with central clearing Tinea corporis, sarcoidosis

Zosteriform (dermatomal)

Following nerve or segment of body Herpes zoster

Polycyclic Interlocking or coalesced circles (formed by enlargement of annular lesions)

Psoriasis, urticaria

Linear In a line Contact dermatitis

Iris/target lesion Pink macules with purple central papules Erythema multiforme

Stellate Star shaped Meningococcal septicemia

Serpiginous Snakelike or wavy line track Cutanea larva migrans

Reticulate Netlike or lacy Polyarteritis nodosa, lichen planus lesions of erythema infectiosum

Morbilliform Confluent and salmon colored Rubeola

BORDER OR MARGIN

Discrete Well demarcated or defined; able to draw a line around it with confidence

Psoriasis

Indistinct Poorly defined; having borders that merge into normal skin or outlying ill-defined papules

Nummular eczema

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Active Margin of lesion shows greater activity than center

Tinea species eruptions

Irregular Nonsmooth or notched margin Malignant melanoma

Border raised above center

Center of lesion depressed compared to edge Basal cell carcinoma

Advancing Expanding at margins Cellulitis

ASSOCIATED CHANGES WITHIN LESIONS

   

 

   

 

 

 

 

 

 

         

     

       

           

           

 

 

         

   

       

   

 

 

     

   

 

 

 

   

 

 

 

 

 

 

     

   

 

 

 

 

 

NATURE OF LESION

DESCRIPTION EXAMPLES

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Central clearing

Desquamation

Keratotic

Punctate

Telangiectasias

Erythematous border surrounds lighter skin

Peeling or sloughing of skin

Hypertrophic stratum corneum

Central umbilication, or dimpling

Dilated blood vessels within lesion blanch completely; may be markers of systemic disease

Tinea eruptions

Rash of toxic shock syndrome

Calluses, warts

Basal cell carcinoma, molluscum

Basal cell carcinoma, actinic keratosis

PIGMENTATION

Flesh

Pink

Neurofibroma, some nevi

Eczema, pityriasis rosea

Erythematous

Salmon

Tan-brown

Tinea eruptions, psoriasis

Psoriasis

Most nevi, pityriasis versicolor

Black

Pearly

Purple

Malignant melanoma

Basal cell carcinoma

Purpura, Kaposi sarcoma

Violaceous

Yellow

White

Erysipelas

Lipoma

Lichen planus

   

         

 

 

   

               

           

   

 

 

     

       

 

   

   

   

       

 

   

   

 

 

 

 

 

 

   

 

Table 28.2

Descriptive Dermatologic Termsa

LESION

Annular

CHARACTERISTICS

Ring shaped

EXAMPLES

Ringworm

Arcuate Partial rings Syphilis

Bizarre Irregular or geographic pattern not related to Factitial dermatitis any underlying anatomic structure

CircularCircinate

Confluent Lesions run together Childhood exanthems

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Discoid Disc-shaped without central clearing Lupus erythematosus

Discrete eczematoid

Lesions remain separate; Inflammation with Eczema tendency to vesiculate and crust

Generalized grouped

Widespread; lesions clustered together Herpes simplex

Iris Circle within circle; bull’s-eye lesion Erythema multiforme (iris)

Keratotic Horny thickening Psoriasis

Linear In Lines Poison ivy dermatitis

Multiform papulosquamou s reticulated

More than one type of shape or lesion Papules or plaques associated with scaling; lacelike network

Erythema multiforme psoriasis Oral lichen planus

Serpiginous Snakelike, creeping Cutaneous larva migrans

           

   

 

 

 

 

     

       

 

 

   

 

   

       

       

Telangiectatic Relatively permanent dilation of superficial blood vessels

Osler‐Weber‐Rendu disease

Universal zosteriformb

Entire body involved Linear arrangement along nerve distribution

Alopecia universalis; herpes zoster

aExamples of different configurations of skin lesions and their descriptions are contained within Table 28.1. bAlso known as dermatomal. From Swartz MH: Textbook of physical diagnosis: history and examination, ed. 6, Philadelphia, 2009, Saunders.

Perform a systematic physical examination before obtaining the majority of the history to provide greater relevance to the information given by the patient. Use gloves when palpating rashes and lesions.

Diagnostic reasoning: Focused history

Is the rash associated with an immediate life-threatening condition?

Key Questions  Do you have a fever?  Are you short of breath?

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• Do you have difficulty swallowing? • Is the rash tender, and does it involve mucous membranes?

Fever Fever is common in viral exanthems (rashes), and the accompanying condition is usually not life threatening. However, fever, irritability, hypotension, and a macular or petechial rash may indicate meningococcemia. Treatment needs to be immediate to be lifesaving.

Allergic reaction Urticarial allergic reactions may be associated with angioedema (swelling) of the extremities, face, lips, tongue, or airway. Other symptoms include cough, wheezing, shortness of breath, and heart palpitations. The sooner symptoms occur after the exposure to the allergen, the more severe the reaction will be. Treatment needs to be instituted immediately.

Rash with mucosal involvement Toxic epidermal necrolysis (TEN), and Stevens­Johnson syndrome are severe mucocutaneous reactions, most often to medications, characterized by extensive necrosis, and epidermis detachment. These conditions are considered variants of a continuum, based on the percentage of body surface involved. TEN is a more severe condition involving more than 30% of the body surface. Reactions include a tender, morbilliform, erythematous rash accompanied by fever, conjunctivitis, oral ulcers, and diarrhea. Immediate hospitalization is required to treat exfoliation of large areas of skin.

Is the rash acute or chronic (recurrent)? Key Questions

• How long have you had this rash? • Have you ever had a rash like this before?

Onset The diagnosis of skin lesions is initially aided by categorizing the lesion as acute, chronic, or recurrent. Acute eruptions, such as urticaria or various fungal rashes (tinea), are classified as such because they have a tendency to be self­limiting with no recurrence after effective treatment. Chronic rashes, such as psoriasis or eczema, may persist or be recurrent with exacerbations and remissions. Box 28.1 shows common rashes categorized by duration. Ascertain the duration of the eruption when symptoms are described by the patient; however, the initial occurrence of a chronic rash may be an acute presenting symptom. Conversely, an acute eruption not optimally treated may become a chronic problem.

Box 28.1

D u r a t i o n o f R a s h

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ACUTE CHRONIC

• Allergic or contact dermatitis • Candida dermatitis (diaper rash, intertrigo) • Erythema infectiosum (fifth disease) • Erythema multiforme • Fixed drug eruptions • Folliculitis • Herpes simplex virus • Herpes zoster/varicella zoster • Impetigo • Infestations (scabies, pediculosis) • Insect bites • Kawasaki disease • Pityriasis rosea • Septicemia (meningococcal) • Scarlet fever • Tinea (corporis, pedis, versicolor) • Urticaria • Viral exanthems (measles)

• Acne vulgaris • Bullous pemphigus • Eczema • Erythema nodosum • Kaposi sarcoma • Mycosis fungoides • Polyarteritis nodosa • Psoriasis • Rosacea • Seborrheic dermatitis • Systemic lupus erythematosus

Where is the rash in its evolution? Key Questions

• What did this look like initially? • Has the rash changed? If so, how? • Has it spread? Where?

Initial presentation Most skin lesions evolve over time, although this varies from minutes with urticaria to weeks or even months with psoriasis or cutaneous T­cell lymphoma.

Change in lesion Determining whether there has been a change from the initial appearance of a lesion provides diagnostic clues. The eruption of pityriasis rosea classically begins with a “herald patch,” a single, scaly, erythematous patch usually on the trunk followed within days by a regional outbreak of numerous smaller erythematous patches, thus providing a key diagnostic clue. The rash may look like that of ringworm, but it appears too quickly to be ringworm. Another example of evolutionary change is the eruption of herpes simplex virus (HSV), which begins with a prodrome of burning, tingling, or itching, followed by the development of small vesicles that later umbilicate, possibly ooze, and eventually crust before healing. A rash may appear in different ways, depending on the point at which evaluation is sought.

Spread The way in which a rash spreads is helpful in diagnosing the specific rash. There are three general ways in which a rash can spread: centripetal, or moving to the center; centrifugal, or moving away from the center; and caudal, or moving down.

What does the presence of pruritus tell me? Key Questions

• Does it itch?

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Itching All dermatoses can be classified into three groups: a small group that always itches, those that never itch, and an intermediate group in which itching is variable (Box 28.2). Pruritus is often reported to be worse at night; during the day, pruritus is less troublesome because the patient is distracted by daily routines. At bedtime the slightest sensation of pruritus may become overwhelming because the patient is focusing on trying to sleep. When the patient scratches the area, histamine is released from the inflammatory cells (especially mast cells), and this causes more pruritus, and an itch–scratch cycle is established.

Box 28.2

I t c h i n g C o m p a r i s o n

ALWAYS ITCH

• Atopic dermatitis • Urticaria • Insect bites • Scabies • Pediculosis • Lichen planus • Chickenpox

MAY ITCH

• Psoriasis • Impetigo • Tinea • Pityriasis rosea

NEVER ITCH

• Warts • Neurofibromatosis • Vitiligo • Nevi

Swimmer’s itch, also called cercarial dermatitis, occurs in areas unprotected by a swimsuit. It is an allergic reaction to a microscopic parasite that burrows under the skin. Seabather’s itch occurs in areas under the swimsuit. Nocturnal pruritus most typically occurs in scabies infestations. Itching in the absence of a rash may be an important clue to internal disease.

What does associated pain tell me? Key Questions

• Is it painful or sore? • Does it burn?

Pain Pain is a rare symptom with skin rashes. Skin lesions that ulcerate or are associated with swelling can be painful. The classic painful rash is associated with herpes zoster (HZ), including postherpetic neuralgia. Severe psoriasis or eczema with fissures and bleeding may also be described as painful by some patients. Soreness is a more common symptom and is associated with numerous rashes. Tender erythema may be associated with TEN.

Burning Burning is infrequently reported. It is most notable preceding the rash in herpes virus infections (e.g., HSV or HZ).

What do associated symptoms tell me? Key Questions

• Do you have a fever? Sore throat? Headache? • How are you feeling in general?

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Fever, sore throat, and headache Fever is a common presenting complaint in infectious diseases accompanied by rash, such as HZ, erythema infectiosum, scarlet fever, endocarditis, or Kawasaki disease. Malaise, sore throat, nausea, or vomiting can occur with mononucleosis.

General health In a patient with a maculopapular eruption, the two most common causes are drug reaction and viral illness. Inquire about viral symptoms, such as fever, malaise, and upper respiratory tract or gastrointestinal symptoms.

Are there possible contacts or sources of contagion? Key Questions

• Does anyone with whom you live or have close contact have something similar? If so, how long have they had it?

• Have you traveled recently? Where? • What do you do for a living? What are your hobbies or leisure activities? • Do you have any pets? Have you been around animals?

Living situation Explore the patient’s living situation. The geographic details of his or her daily activities may help provide diagnostic clues, particularly for rashes caused by infectious or infestation mechanisms. Children, in particular, may contract scabies, pediculosis (lice), or impetigo by direct contact in school or daycare.

Travel A patient may develop a rash weeks or months after travel exposure. Diseases endemic to other parts of the world may have presenting symptoms of rash, including erythema nodosum, which is common in Southeast Asia, or leprosy, which is common in many parts of the world, especially in tropical and subtropical climates. Both eruptions may also occur secondary to tuberculosis. About 40% of erythema nodosum is idiopathic and can be related to inflammatory disease and malignancy. Leishmaniasis is a parasitic infection spread by the bite of phlebotomine sand flies. It is seen in the tropics, subtropics, and southern Europe. Camping trips to wooded areas, especially in the Eastern and upper Midwestern United States, may result in a bite by a deer tick, causing Lyme disease, the leading vector­borne infectious disease. The resultant skin eruption in Lyme disease is known as erythema chronicum migrans, which begins 4 to 20 days after the bite of the tick; only one third of patients remember being bitten. Rocky Mountain spotted fever (Rickettsia rickettsii) is transmitted by a tick bite and is common in the south Atlantic region of the United States. Initial symptoms are nonspecific; later symptoms are a petechial rash and fever, usually requiring hospitalization.

Other exposures Outdoor occupations or leisure activities may expose individuals to a variety of sources for rashes and lesions, including insect bites as well as allergic or contact dermatitis from poison ivy, excessive sun exposure, and chemical substances. People exposed to animal skins contaminated with Bacillus anthracis may develop cutaneous anthrax, which is characterized by lesions that evolve from a papule through a vesicular stage to a depressed eschar. Sun exposure can also worsen chronic eruptions such as rosacea or the malar butterfly rash in systemic lupus erythematosus. Ringworm is common in farmers and ranchers who work with cattle.

Pets Flea bites produce an urticarial lesion with a central punctum. The reaction is an immunologic one, making it different in each individual. Bites are usually on the legs; infants may have bites on the arms or trunk. New lesions may appear daily, and itching is variable but sometimes intense. Fleas on a cat or dog are usually the culprits. An atypical form of scabies can be transmitted from dogs to humans; the presenting symptom is usually a single lesion in an area under occlusion and it lasts about 1 to 2 weeks.

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Is there anything that exacerbates or triggers the reaction? Key Questions

• Does anything seem to make this worse? • Do you have any known allergies?

Triggers Patients often easily identify aggravating factors. Any rash involving vasodilation will become more vivid and likely more pruritic with heat exposure, whether via sunlight, sweating, or a hot shower. Localized eruptions, especially on the hands or forearms, prompt many patients to consider chemicals or other products as causes. People with eczema whose hands are frequently exposed to water are vulnerable to the development of irritant eczema on the exposed skin. Some foods occasionally exacerbate skin lesions. Rosacea is a vasomotor instability disorder characterized by exacerbation with dietary consumption of vasodilators such as coffee, tea, alcohol, or spicy foods. Stress, whether physiological (e.g., menstruation, pregnancy) or psychological, is widely believed to trigger or worsen many chronic rashes, especially eczema, acne, and psoriasis. Stress also may facilitate recurrent eruptions of HSV.

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E V I D E N C E - B A S E D P R A C T I C E

What Is the Evidence About the Prevention and Diagnosis of Melanoma? This review summarizes findings from 17 systematic reviews and two guidelines on skin cancer between April 2008 and 2009. Melanoma primary­prevention measures, such as education, are more likely to be successful in younger children than adolescents. The evidence does not currently support population screening for melanoma by whole­body examination. Sunburn later in life increases the risk of melanoma as much as sunburn early in life. Superior diagnostic accuracy of dermoscopy over naked­eye examination for melanoma was mixed.

Reference: Macbeth et al, 2011.

Could this rash be caused by a medication? Key Questions

• Are you taking any medications (prescription or over­the­counter medications)? • Do you have any medication allergies? • Have you had a recent vaccination?

Medication and medication allergies There are four types of dermatologic side effects of drugs: light sensitivity (e.g., photodermatitis), allergic reactions (e.g., urticaria, fixed drug eruptions, morbilliform eruptions), commensal skin eruptions (e.g., pityriasis versicolor in a patient on systemic corticosteroids), and worsening of existing skin eruptions (e.g., tinea eruptions mistakenly treated as eczema with topical corticosteroids). Medications used after the onset of a rash may be irritants or sensitizers and worsen the condition.

Recent vaccination Infants and children who have recently had a measles vaccination may display a rash 10 to 14 days after immunization.

Is there a significant dermatologic family history? Key Questions

• Does anyone in your family have chronic skin problems?

Family history A family history of dermatologic problems may add insight to the diagnosis. Atopic disease (eczema, asthma, hay fever) tends to cluster in families. Psoriasis, seborrheic dermatitis, and rosacea are also frequently noted to have a familial inheritance pattern. Multiple café­au­lait spots with a positive family history for neurofibromatosis can help identify children with this autosomal dominantly inherited disease.

Diagnostic reasoning: Focused physical examination

Look at all the skin and mucous membranes A “peephole” diagnosis should be avoided; the whole organ should be examined. If the patient is not fully undressed, relevant lesions could be missed. However, it is useful to select one typical well­defined lesion to describe in detail followed by an orderly and sequential system of examination so that no areas of the body are missed. The feet should always be examined in the presence of hand dermatitis so that a hypersensitivity

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reaction to a tinea infection or a concomitant hand tinea will not be missed. Erythema in dark­skinned people may be difficult to appreciate; it often is seen as postinflammatory hyperpigmentation.

Inspect for distribution Determine if the lesion is widespread or localized, unilateral or bilateral, symmetrical or asymmetrical. Symmetrical lesions commonly have internal causes (e.g., eczema, psoriasis); asymmetrical lesions have external causes (e.g., bacterial or fungal infections, allergic contact eczema). Is the lesion predominantly on the flexor (as in atopic dermatitis) or extensor (as in psoriasis) surfaces? A rash on the soles or palms occurs with erythema multiforme, secondary syphilis, and rickettsial infections. Determine if the distribution is confined either to protected areas or to light­exposed areas such as in collagen­vascular diseases, photosensitive reactions to drugs, and airborne contact dermatitis. Is the lesion predominantly centrifugal (affecting the extremities), as seen in erythema multiforme, Rocky Mountain spotted fever, and insect bites, or centripetal (sparing the extremities and concentrated on the trunk)? Intertriginous distribution (neck, axilla, groin) is found in candidiasis, some inflammatory fungal infections, and some forms of psoriasis.

Inspect the mouth Drug eruptions from sulfonamides, penicillin, streptomycin, quinine, and atropine often have associated mucosal erosions (enanthems) and crusts. Mucosal involvement is common in hand and foot lesions (e.g., hand, foot and mouth disease), herpes, and syphilis. Oral lesions occur in lichen planus, autoimmune blistering diseases, and malignancies such as squamous cell carcinoma.

Inspect the hair In children, a triad of hair loss, scaling, and lymphadenopathy is diagnostic of tinea capitis. A high index of suspicion is warranted in inner­city urban areas, where the condition is common.

Evaluate for hair loss that is diffuse or localized and compare areas such as the temporal and crown region to the occiput. Psoriasis and seborrheic dermatitis may present as scaling and desquamation. A hair pull test will reveal any increased hairs shed with a gentle pull.

Palpate the skin Palpate skin lesions to assess for tenderness, texture and consistency, firmness, fluctuance, and depth. Smooth skin has no irregularity. Uneven skin has fine scaling or some warty lesions. Rough skin feels like sandpaper and is characteristic of keratin (horn) or crusts. Assessing the superficial skin for texture is done by palpation with the fingertips. Deeper palpation is done using the thumb and index fingers. Soft skin feels like the lips, normal skin like the cheeks, firm skin like the tip of the nose, and hard skin like the forehead. The depth of the lesion determines if it is on the surface or located within the dermis or subcutaneous tissue. An indurated base is a thickening in the depths of the lesion rather than on the surface.

Palpate the regional lymph glands Many viral exanthems present with rash and lymphadenopathy. Palpation of the regional lymph glands may be of assistance in the diagnosis if neoplasm is suspected.

Perform an abdominal examination The detection of hepatic or splenic enlargement may assist in the diagnosis of a systemic cause of skin disorders.

Laboratory and diagnostic studies

Diascopy Diascopy is used to assess for blanching on pressure and is accomplished by pressing a glass or clear plastic slide on the lesion and observing for color changes. It is used to determine whether a lesion is vascular (inflammatory or congenital), nonvascular (nevus), or hemorrhagic (petechia or purpura). Diascopy is most

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helpful in evaluating purpuric lesions; blood that is outside vessels (as in petechiae) will not blanch, but blood that is entrapped within dilated vessels (as in telangiectasias) will blanch.

Dermoscopy Dermoscopy uses a skin surface microscope (dermatoscope) with or without the application of oil on a skin lesion to illuminate and magnify a lesion. This technique allows a more detailed inspection of the surface of pigmented skin lesions to confirm a diagnosis of melanoma and to determine which skin lesions require biopsy or removal. Dermoscopy requires special training and expertise.

Wood’s light Long­wave ultraviolet (UV) light is used in the diagnosis of lesions caused by fungal

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infections. Many but not all fungal rashes fluoresce different colors. Trichophyton organisms and Tinea tonsurans, dermatophytes that are frequently identified in tinea eruptions in the United States, do not fluoresce; Microsporum organisms, which can cause tinea eruptions, do fluoresce.

Skin scraping and potassium hydroxide preparation Microscopically examine a sample of cells retrieved from a lesion, assessing for the presence of fungal or dermatophytic spores and hyphae. The lesion should be gently scraped using a scalpel (collect cells from an active area such as the border of the lesion); the cells are treated with a drop of 20% potassium hydroxide (KOH) and then warmed or allowed to stand a few minutes to soften the keratin. The addition of 40% dimethyl sulfoxide (DMSO) to the KOH solution accelerates diagnosis. Chlorazol black E stain highlights fungal hyphae as dark, blue­black against a light gray background.

Tzanck smear In a Tzanck smear, an indirect test for herpes virus infections (herpes simplex virus, herpes zoster), cells are retrieved by swabbing the base of a lesion (usually a vesicle), smearing it onto a glass slide, and then staining it with Giemsa or Wright solution. Examined microscopically, the presence of multinucleated giant cells confirms the presence of herpes virus but cannot differentiate between herpes simplex virus or varicella­zoster virus infections. Viral culture is diagnostic.

Bacterial or viral culture For a bacterial culture, exudate from a lesion is collected on a sterile swab and cultured for growth. Gram staining may also be done. When a bacterial isolate is known, antibiotic sensitivity testing is performed.

For a viral culture, cells from the base of a lesion (usually a vesicle) are collected on a Dacron swab and cultured for identification of viral infections, particularly HSV or HZ.

Punch biopsy In a punch biopsy, a cylindrical­shaped tissue sample is assessed histopathologically for identification. Select a punch size about 3 to 4 mm larger than the lesion or sample an active area if the lesion is large. First the skin is cleansed and local anesthesia is administered. While stretching the skin with the other hand, gently rotate the biopsy instrument while exerting slight downward pressure. When well into the dermis, remove the punch and excise the sample at its base. The defect may be closed using electrocautery, with suture(s), or left open to heal by second intention. Place the fresh specimen on gauze with normal saline for immediate transport to pathology to be processed. If the specimen is being sent for culture or immunofluorescent staining, place in a preservative such as formaldehyde solution.

Excisional biopsy In excisional biopsy, a tissue sample is assessed histopathologically for identification. Excise the entire lesion, usually making an elliptical incision around the lesion beyond its margins. Excise the base and close the defect with sutures or cauterize bleeding vessels. Handle the specimen in the same manner used for a punch biopsy.

Differential diagnosis The following conditions represent many of the most common skin eruptions observed in primary care.

Follicular eruptions

Acne vulgaris Acne presents as a chronic eruption of the pilosebaceous unit, with noninflammatory lesions (open or closed comedones) or inflammatory lesions (e.g., papules, pustules, cysts), and is most commonly a problem of adolescents. Its distribution follows that of the sebaceous glands: face, neck, chest, back, and upper arms. Neonatal acne first occurs between 2 and 4 weeks of age, lasting until 4 to 6 months of age. Persistence beyond

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12 months may indicate endocrine dysfunction. Dark­skinned individuals need aggressive treatment to prevent postinflammatory hyperpigmentation.

Rosacea Rosacea is a vasomotor instability disorder characterized by sebaceous gland hypertrophy, papules, pustules, persistent erythema, and telangiectasias. It shows a predilection for the face.

Infectious eruptions

Impetigo Impetigo presents as a superficial pustular, bullous, or nonbullous eruption followed by crusting (often honey colored). The causative organism is usually staphylococci or streptococci. Contagion occurs via direct inoculation. It is typically a localized eruption that can occur anywhere on the body, with a predilection for the face and trunk.

Folliculitis Folliculitis is a superficial pustular infection of the hair follicles. Causative organisms are usually staphylococci and occasionally streptococci or gram­negative organisms, including Pseudomonas, Klebsiella, and Proteus spp. It is typically a localized eruption that can occur anywhere on the body, with a predilection for hairy areas and flexural regions.

Furuncle A furuncle, often referred to as a boil, is a more extensive infection secondary to folliculitis (see Folliculitis).

Carbuncle A carbuncle is an abscess of conjoined or adjacent furuncles (see Furuncle).

Macular and papular eruptions

Erythema infectiosum (fifth disease) Fifth disease, also known as slapped cheek disease, is a systemic illness of sudden onset characterized by a coalescing, red, maculopapular eruption on the face. A reticular eruption occurs on the extremities 2 to 3 days later. The causative organism is parvovirus B19. This is a self­limiting condition.

Children with underlying hemolytic anemia may experience an aplastic crisis.

Measles (rubeola) Measles are caused by a viral exanthem, and the systemic illness that results is characterized by a fine, erythematous, morbilliform eruption on the face that spreads to the trunk over 4 to 7 days, and becomes confluent and reticulate. White patches on red mucosa (Koplik spots) appear on the buccal mucosa. Cough, purulent coryza, photophobia, and fever precede the rash. This is a self­limiting condition and less common with widespread childhood immunization.

Rubella Rubella results from a viral exanthem similar to measles, starts as fine macules and papules on the face, and progresses caudally within 24 hours. Lymphadenopathy of postauricular nodes is characteristic of this disease.

Pityriasis rosea The presenting symptom of pityriasis rosea is a rapidly evolving papulosquamous eruption of possible viral etiology. An initial “herald patch” is characteristic followed within days by numerous faintly erythematous patches on the trunk and upper extremities (“T­shirt and shorts” distribution). The lesions follow the lines of cleavage and have a “Christmas tree” pattern on the back. The patches demonstrate fine scaling, and mild to severe pruritus may be present. It is more common in the spring and fall and among adolescents. In African American children, the eruption may consist only of occasional oval lesions along the cleavage lines. The

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remaining lesions are discrete, scattered follicular or nonfollicular papules over the trunk and proximal extremities. The face may also be involved.

Scarlet fever Scarlet fever is a systemic illness associated with group A β­hemolytic streptococci (GABHS) (strep throat)

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and is easily treatable with antibiotics. It is characterized by a macular erythema of the face (flushing), except around the mouth (circumoral pallor), followed by a disseminated fine papular erythema (scarlatiniform), which may then desquamate. The rash is intensified in the flexor folds (Pastia lines). Associated symptoms are sore throat, malaise, fever, circumoral pallor, and a white or strawberry tongue. Scarlet fever is a rarely occurring infectious disease in the United States.

Roseola Roseola is a viral infection caused by human herpesvirus 6. It is characterized by 2 to 3 days of sustained fever in an irritable infant who otherwise appears well. Mild edema of the eyelids and posterior cervical lymphadenopathy are occasionally seen. After the patient’s temperature decreases, a pink, morbilliform, cutaneous eruption appears transiently and fades within 24 hours. This is a self­limiting condition.

Vesicular and bullous eruptions

Hand, foot, and mouth disease Coxsackievirus A16 is the causative organism of this viral exanthem and systemic illness. Painful mouth ulcers followed by painful white vesicles with a surrounding erythema on the fingers, palms, toes, and soles characterize the condition. Patients usually have a low­grade fever, sore throat, and malaise for 1 to 2 days. Some develop submandibular or cervical lymphadenopathy. This is a self­limiting condition.

Insect bites Mosquito and horsefly bites can cause a common blistering reaction that is surrounded by faint erythema, central pallor if swollen, and usually a visible central punctum. The bites may be arranged in groups if they are multiple. The lesions are pruritic or sore; the condition is self­limiting. The deer tick bite causes a bull’s­eye rash at the site of the bite.

Bed bugs The bed bug, Cimex lectularius, is a pest that feeds on blood, causes itchy bites, and generally irritates their human hosts. The Environmental Protection Agency, Centers for Disease Control and Prevention, and United States Department of Agriculture all consider bed bugs a public health pest. However, bed bugs are not known to transmit or spread disease.

Bites on the skin are a poor indicator of a bed bug infestation. Bed bug bites can look like bites from other insects (e.g., mosquitoes, spiders), rashes (e.g., eczema, fungal infections), or even hives. Some people do not react to bed bug bites at all. Bed bug bites can be misidentified, which gives the bed bugs time to spread to other areas of the house.

A more accurate way to identify a possible infestation of bed bugs is to look for physical signs of the pest. For example, noting spots on bedding (about this size: •) that are bed bug excrement is one of the earliest and most accurate methods. The increase in bed bugs in the United States may be caused by more travel, lack of knowledge about preventing infestations, increased resistance of bed bugs to pesticides, and ineffective pest control practices.

Herpes simplex virus Herpes simplex virus lesions have grouped vesicles that are surrounded by an erythematous base, with discrete, well­demarcated areas that later crust. The condition is associated with soreness or pain and may be preceded by tingling. There is a predilection for lips and genitalia. Recurrences in the same location are common and usually milder.

Herpes zoster (shingles) Herpes zoster lesions present as clustered vesicles that follow a dermatome. Lesions are surrounded by an erythematous base, with discrete, well­demarcated lesions that later crust. Intense burning and pain often precede the eruption. Herpes zoster along the ophthalmic branch of the trigeminal nerve requires an immediate ophthalmology visit, as this can lead to zoster of the eye and resultant blindness.

Varicella zoster (chickenpox)

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Varicella lesions are discrete vesicles with a disseminated distribution; lesions develop in crops or in succession. Vesicles later crust, and occasionally secondary impetigo develops. The illness is associated with malaise and fever. This is a self­limiting condition. Varicella zoster can later be reactivated as shingles in patients over 50 or those who are immunosuppressed. A shingles vaccination is recommended for all adults 60 years and older to reduce the risk of shingles.

Fungal infections

Candidiasis Candidiasis is a yeast that produces rashes at a variety of sites; these rashes are called vulvovaginitis, thrush, intertrigo (groin, axilla, gluteal), and diaper dermatitis. The lesion is an erythematous maculopapular eruption that is well demarcated, occasionally with satellite lesions (pinpoint papules) at the periphery with maceration in moist areas. It is associated with mild to intense pruritus; the causative organism usually is Candida albicans.

Tinea Tinea is a fungal eruption that causes rashes at a variety of sites: body (corporis), foot (pedis), beard (barbae), groin (cruris), and scalp (capitis). Lesions have erythematous scaling areas with a discrete border and central clearing that is often associated with pruritus or soreness. The causative organisms are Trichophyton, Microsporum, and Epidermophyton spp.

Pityriasis (tinea) versicolor Pityriasis versicolor is a yeast infection characterized by a macular eruption of many colors, hypopigmentation to hyperpigmentation, and fine scaling. Macules begin insidiously, may take weeks to months to fully develop, and may coalesce. The condition is usually asymptomatic but occasionally pruritic. There is a predilection for a sebaceous gland distribution (neck, trunk). The causative organism is Pityrosporum orbiculare (Malassezia globosa). Repigmentation may take years or may never occur. Recurrences are common.

Immunologic and inflammatory eruptions

Eczema Eczema is a chronic relapsing inflammatory condition that can take several forms (atopic, nummular, or dyshidrotic). Erythematous macules, papules, and vesicles that occasionally weep or crust characterize eczema. When severe, eczema may produce fissuring and bleeding. It is associated with mild to intense pruritus. In dark­skinned people, scaling and dryness associated with eczema give an “ashy” appearance to the skin.

Contact or allergic dermatitis Contact dermatitis is an inflammatory reaction to many substances (e.g., poison ivy, nettles, rubber, nickel). Papulovesicular or bullous eruptions surrounded by erythema, with weeping of exudate (noncontagious), are characteristic of the condition. It may be associated with moderate to intense pruritus.

Psoriasis Psoriasis is a chronic, relapsing autoimmune disorder characterized by well­demarcated erythematous plaques, patches, and papules, which typically present with silvery scales. There is a predilection for the elbows, knees, hands, nails (pitting), scalp, and gluteal cleft. The condition may be pruritic or sore. The lesions may demonstrate Auspitz sign: pinpoint bleeding when the surface is scraped.

Seborrheic dermatitis Seborrheic dermatitis is a chronic, relapsing disorder characterized by erythematous scaling

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patches, which are poorly demarcated and may be pruritic. There is a predilection for the scalp, nasolabial folds, ears, face, central chest, and genitals. The condition is aggravated by cold weather, dry skin, and stress.

Allergic reactions

Erythema multiforme Erythema multiforme is an immune complex disorder involving the skin and occasionally the mucous membranes. Iris (target) lesions appear on the extremities and desquamation often follows. Common causes include medications (especially sulfonamides, penicillins, barbiturates, salicylates), histoplasmosis, Mycoplasma, HSV, mononucleosis, hepatitis B, and malignancies. Erythema multiforme minor is often self­limited. More severe forms are Stevens­Johnson syndrome, characterized by widespread involvement with vesicobullous lesions and TEN. Both involve the mucous membranes, conjunctiva, and urethra. The more severe forms can involve the lungs, gastrointestinal tract, and kidneys.

Urticaria Urticaria is characterized by a well­demarcated, usually disseminated eruption that is evanescent over minutes to about 24 hours. The condition usually has an asymmetrical distribution.

Neoplastic eruptions

Malignant melanoma Melanoma is an aggressive cancer with a tendency to spread rapidly and metastasize early. Characterized by asymmetry (half of a mole or lesion does not look like the other half), melanoma has an irregular, scalloped, or not clearly defined border with a color that varies or is not uniform (whether the color is tan, brown, black, white, red, or blue). The diameter is usually larger than 6 mm. However, any change in the size of a mole should be viewed with suspicion. The three most significant risk factors for the development of melanoma include a history of melanoma in a first­degree relative, a large number of moles (>50–100), and atypical moles as designated by biopsy. Other factors that increase the risk of melanoma include adulthood, blond or red hair, blue or light­colored eyes, changed or persistently changing mole, white race, fair complexion, freckles, personal history of melanoma, immunosuppression, inability to tan, severe sunburns in childhood, and presence of a congenital mole. In addition, UV light from tanning beds can both cause melanoma and increase the risk of a benign mole progressing to melanoma.

Basal cell carcinoma Basal cell carcinoma usually appears as a small, fleshy bump or nodule on the head, neck, or hands. Occasionally, these nodules may appear on the trunk of the body, usually as flat growths. These basal cell tumors do not spread quickly. It may take many months or years for one to reach a diameter of 1/2 inch. Untreated, the carcinoma will begin to bleed, crust over, and then repeat the cycle. Although this type of cancer rarely spreads to other parts of the body, it can extend below the skin and cause considerable local damage. The cure rate for basal cell carcinoma (sometimes referred to as nonmelanoma carcinoma) is 95% when properly treated.

Squamous cell carcinoma Squamous cell carcinoma presents as an indurated papule, plaque, or nodule with a thick scale that is often eroded, crusted, or ulcerated. It can be found on sun­exposed skin surfaces, in areas of radiodermatitis, or on old burn scars. Although slow growing, squamous cell carcinomas arising on the lip, mouth, or ears may be associated with regional lymphadenopathy and metastasis. If promptly and properly treated, it has a cure rate of 95%.

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DIFFERENTIAL DIAGNOSIS OF Common Causes of Rashes and Skin Lesions

CONDITION CHARACTERISTICS

FOLLICULAR ERUPTIONS

Acne vulgaris Comedones and/or papules, pustules, cysts

Flushing, persistent redness, sebaceous hyperplasia, erythematous papules, telangiectasias, ocular involvement in up to 40%

INFECTIOUS ERUPTIONS

Any hair­bearing body surface, but especially scalp, beard, legs, axillae

Impetigo

Folliculitis

Furuncle

Rosacea

Vesicular infection; honey­ colored crusts and erosions

Superficial perifollicular papules and pustules

Very tender, deep­seated inflammatory nodule that develops from folliculitis

Carbuncle Multiple coalescing furuncles

MACULAR OR PAPULAR ERUPTIONS

Bright­red rash or “slapped cheeks,” followed by diffuse maculopapular rash on trunk and extremities, leading to a lacy appearance as exanthem fades

Erythema infectiosum

Measles

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DISTRIBUTION OR PROGRESSION

Face, neck, back, chest, upper arms

Symmetrical, usually face only; may involve eyes

Face; any area of body with a minor wound, especially excoriated lesions

Same as folliculitis

Same as furuncle

Cheeks, then trunk and extremities

DIAGNOSTIC ASSOCIATIONS

STUDIES

Onset of puberty, topical steroids, anabolic steroids, systemic corticosteroids, lithium, phenytoin

Topical steroids, systemic corticosteroids

Usually none

Usually none

Scratching as a result of insect bites, atopic dermatitis, scabies

Bacterial culture

Shaving, hot tubs, contact with mineral oils, occlusive dressings

Bacterial culture

May have fever Incision and drainage for bacterial culture

Same as furuncle Same as furuncle

Aplastic anemia in IgM, IgG can be children with measured underlying hemolytic anemias; fetal hydrops has been reported in pregnant women infected with parvovirus B19

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DISTRIBUTION DIAGNOSTIC

CONDITION CHARACTERISTICS OR ASSOCIATIONS STUDIES

PROGRESSION

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Patient develops three Cs: cough, coryza, and conjunctivitis; Koplik spots are evident on buccal mucosa; rash begins with spike of convalescent fever; rash is centripetal in distribution, possibly becoming hemorrhagic in severe cases

Rubella Tender lymphadenopathy of postauricular, posterior occipital nodes; maculopapular and confluent rash that is lacy and not pruritic; rash lasts 3 days

Rash begins on face and spreads to trunk and extremities within first 24 hr

Pityriasis rosea

Scarlet fever

Fine, mildly erythematous papules and sandpaper­like rash found on trunk

Roseola High fever for 3–4 days in infants and young children; as fever returns to normal, a diffuse maculopapular rash erupts

Rash begins on trunk and quickly spreads to arms, face, neck, and legs

Rash starts on neck and ears faintly, then covers face, arms, and chest; on second day rash covers lower torso and legs; on third day rash is on feet and face; rash begins to fade on the fourth day

Multiple oval erythematous lesions with an inner fine circle of scale; ovals line up along skin cleavage lines on trunk, producing a Christmas tree –like pattern

Trunk, proximal extremities, rarely on face; rash is preceded by a “herald patch,” appearing from a few days to 3 wk before generalized eruption

Rash begins in axillae, groin, and neck; it avoids face, but there is circumoral pallor

VESICULAR AND BULLOUS ERUPTIONS

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Abdominal pain, otitis media, and bronchopneumonia are commonly associated; severe cases can cause encephalomyelitis

Infection with virus while pregnant results in congenital rubella

More common in spring and fall

Strawberry tongue; Pastia lines: areas of linear hyperpigmentation in deep creases

Posterior cervical lymphadenopathy

None

IgM can be measured for measles as well as acute and IgG titers

Confirmation by acute and convalescent IgG titers, or by direct measurement of rubella IgM antibody

If present on palms and/or soles and history warrants, check RPR to rule out secondary syphilis

Culture for group A streptococci

None

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Hand, foot, and mouth disease

Insect bites

Bed bugs

Herpes simplex virus

Herpes zoster

Varicella zoster

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Systemic illness caused by coxsackievirus A16; painful white vesicles with surrounding red halo

Flea, tick bites most common; intensely pruritic eruption, usually in groups of three; bull’s­eye rash

Bites may be present, examine bed for small reddish brown spots

Primary infection with grouped vesicles on an erythematous base at site of inoculation; regional lymphadenopathy; may be preceded by prodrome of tingling, itching, burning, or tenderness

Unilateral pain, itching, or burning preceded by 3–5 days of eruption of vesicles or bullae; followed by crusting and erosions

Painful mouth ulcers followed in 24 hr by painful vesicles on fingers, palms, toes, and soles

Lower legs, but may appear anywhere on body if pets allowed on furniture or beds

General distribution

Can occur anywhere on body, but most common areas are genitals, thighs, mouth, lips, and chin; may be disseminated in patients who are immunocompromised

Can occur anywhere on body but is unilateral, following a dermatomal pattern; requires prompt referral to ophthalmologist if eye involved (Note: See lesion on tip or side of nose for indication.)

Low­grade fever, sore throat, and malaise; cervical and submandibular lymphadenopathy possible

Exposure to dogs or cats, or to carpeted areas previously in contact with infected animals; outdoor exposure

Travel, sleeping in a different bed

Other STIs, HIV; triggered by sun, stress, fatigue, fever, trauma

Immunosuppression, older age, local trauma in children

Viral culture, Tzanck smear

Confirmatory biopsy occasionally needed

Observe environment for bugs, stains; implement eradication measures

Viral culture Tzanck smear; screen for STIs, HIV if history warrants

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Generalized pruritic vesicular lesions that are in different stages of healing; erythematous vesicles, ruptured vesicles, and crusted vesicles with scabs

FUNGAL INFECTIONS

Beefy­red, well­ demarcated plaques, often with scaling edge and satellite lesions; intertriginous areas may also show erosions and maceration

Variable, depending on body part affected; hair: scaling, hair loss, pustules; skin: red, scaly patch that may develop central clearing; feet: vesicles or bullae

Candidiasis

Tinea

Pityriasis Variably colored (tinea) white to pink to versicolor brown scaling,

round or oval macules of varying sizes; often coalescing to form large areas of discoloration

Lesions usually begin on trunk and spread to face and proximal extremities

Diaper area in infants, body folds, mucosal surfaces, nails, and nail folds

Herpes zoster occurs with reactivation of virus

Immunocompromised, diabetes, steroid inhalants, pregnancy, oral contraceptives, antibiotics, systemic and topical steroids

Skin, hair, feet, nails

KOH, culture

Upper trunk, axillae, neck, upper arms, abdomen, thighs, genitals

Heat, humidity, tropical climates, exercise, systemic corticosteroids, seborrheic dermatitis

KOH shows hyphae and spores in “spaghetti and meatballs” pattern

Immunocompromised, systemic corticosteroids, farmers and others with animal contact, hot humid weather with tight clothing or occlusive footwear

ELISA titers can confirm acute infection

KOH, culture

IMMUNOLOGIC OR INFLAMMATORY ERUPTIONS

Eczema or atopic dermatitis

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Erythema, papules, vesicles, scaling, excoriations, crusts, pruritus always present

Vesicles and erosions with edema and inflammation, giving way to crusts and lichenification; pruritus

Psoriasis

Seborrheic Chronic scaling, dermatitis flaking,

erythematous dermatitis; variable pruritus

Contact or allergic dermatitis

ALLERGIC REACTIONS

Erythema Hypersensitivity multiforme reaction seen

as annular target or iris lesions

Urticaria Transient wheals that may be acute or chronic (lasting >6 wk);

Well­demarcated, ham­colored plaques and papules with silvery scale; chronic, recurrent pruritus is common

Symmetrical; infant: face, flexures; children: flexural creases; adults: may be discrete round patches or be regionalized to specific area

Localized, often asymmetrical; may be generalized with airborne allergens or poison ivy; linear pattern with plant dermatitis

Favors elbows and knees, scalp; intertriginous areas may involve nails

Areas where sebaceous glands are most active: face, scalp, eyebrows, eyelashes, body folds, ear folds, presternal area, mid and upper back, genitalia

Begins on upper extremities and trunk

Localized, regional, or generalized

Personal or family history of asthma, seasonal allergies, and eczema; secondary colonization with Staphylococcus aureus or HSV

Occupational, recreational pursuits

Streptococcal infection, arthritis, HIV infection, medications, alcohol, family history

Atopic history, HIV infection

Herpesvirus, Mycoplasma pneumoniae infections, drugs (especially sulfonamides)

Angioedema may also be present, may be life threatening; chronic infection, SLE, lymphoma

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Serum IgE; culture for bacteria or HSV if indicated

Patch testing

ASO titer or strep culture if indicated; HIV if indicated; biopsy

HIV if indicated

Skin biopsy may assist in diagnosis; chest film for Mycoplasma

Biopsy; general medical workup to rule out underlying

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Malignant melanoma

Basal cell carcinoma

Squamous cell carcinoma

individual systemic lesions tend to disease in come and go chronic within hours; urticaria pruritic

NEOPLASTIC ERUPTIONS

Skin biopsy, excisional biopsy

Skin biopsy

Skin biopsy, excisional biopsy

Asymmetrical border, irregular, has color variation within lesion and is >6 mm

Papular or nodular lesions, with raised pearly borders, and numerous superficial telangiectases

Indurated papule, plaque, or nodule; may be eroded, crusted, or ulcerated

Anywhere on body, including scalp

Sun­damaged areas; also seen in covered areas when there is genetic predisposition to basal cell carcinoma

Sun­damaged areas, areas of radiodermatitis, old burn scars; can occur anywhere on body

Usually asymptomatic, unless bleeding, ulceration, discharge present

Usually asymptomatic

Usually asymptomatic; can be associated with HPV, immunosuppression, topical nitrogen mustard, oral PUVA, chronic ulcers, industrial carcinogens, arsenic

ELISA, enzyme-linked immunosorbent assay; HIV, human immunodeficiency virus; HPV, human papillomavirus; HSV, herpes simplex virus; IgG, immunoglobulin G; IgM, immunoglobulin M; KOH, potassium hydroxide; PUVA, psoralen plus ultraviolet A (light therapy); RPR, rapid plasma regain; SLE, systemic lupus erythematosus; STI, sexually transmitted infection.

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