Myotonic Dystrophy

Myotonic Dystrophy: Genetic Disorder Affecting Muscle Function and Multiple

Organs

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

Providing genetic counseling assists family planning and addresses anticipation concerns.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

and occupational therapies optimize muscle function and mobility, especially in ambulatory

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Providing genetic counseling assists family planning and addresses anticipation concerns.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Providing genetic counseling assists family planning and addresses anticipation concerns.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

The genetic defect involves unstable expansion of noncoding repeats that accumulate

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

could enable precision management based on individual molecular and clinical profiles over

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

The genetic defect involves unstable expansion of noncoding repeats that accumulate

amongst generations, demonstrating anticipation wherein earlier generations display onset

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Providing genetic counseling assists family planning and addresses anticipation concerns.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

The genetic defect involves unstable expansion of noncoding repeats that accumulate

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

could enable precision management based on individual molecular and clinical profiles over

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Providing genetic counseling assists family planning and addresses anticipation concerns.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

The genetic defect involves unstable expansion of noncoding repeats that accumulate

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

neuromuscular condition.

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

affecting facial, finger flexor and distal leg muscles. Additional DM signatures are frontal

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

Providing genetic counseling assists family planning and addresses anticipation concerns.

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

basis, spectrum of clinical manifestations, diagnosis and management of this complex

The genetic defect involves unstable expansion of noncoding repeats that accumulate

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

binding proteins MBNL1/2, sequestering them in nuclear foci. While DM2 involves CCTG

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

weakness of facial, handgrip and foot dorsiflexor muscles. Electromyography detects

myotonic discharges, fibrillations and positive sharp waves. Echocardiography assesses left

ventricular hypertrophy, conduction blocks or arrhythmias. Pulmonary function testing

evaluates restrictive defects while endocrine workup addresses diabetes, hypogonadism and

others. Genetic testing confirms the mutation type and trinucleotide repeat sizing in

leukocytes.

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Pharmacotherapy trials medications like mexiletine, tocainide or phenytoin for myotonia.

time. Understanding tissue-specific splicing disruptions also provides insights into multi-

organ manifestations.

With improved recognition and care, life expectancy increases but DM1 patients require

multidisciplinary surveillance due to the progressive nature and variable involvement.

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

The genetic defect involves unstable expansion of noncoding repeats that accumulate

amongst generations, demonstrating anticipation wherein earlier generations display onset

symptoms. In DM1, expansions of 50-1500+ CTG repeats interfere with normal CUG-

repeats over 75 that bind MBNL proteins with lower affinity. The RNA toxicity results from

dysregulated alternative splicing across the transcriptome via defective developmentally

regulated post-transcriptional processing.

Classic myotonia presents as delayed muscle relaxation following contraction, worse upon

initial effort or cold exposure. Myopathy causes progressive generalized weakness especially

balding, cataracts, cardiac conduction defects and endocrine dysfunction like insulin

resistance or hypogonadism. Facial appearance reflects extraocular, orbicularis oris and

temporalis muscle weakness. Respiratory and swallowing issues can develop later due to

chest wall and bulbar involvement.

Neurological examination finds diminished deep tendon reflexes, frontal release signs,

Treatment consists of symptomatic measures tailored to specific organ involvement. Physical

and occupational therapies optimize muscle function and mobility, especially in ambulatory

DM1 patients. Non-invasive ventilation supports breathing nocturnally. Cardiac devices pace

or defibrillate when needed. Cataract extraction improves vision. Metformin and insulin

sensitize glucose regulation. Testosterone or fertility counseling address hypogonadism.

Research areas aim to arrest or reverse disease pathogenesis, given no cure exists. Antisense

oligonucleotides like Eplontersen target the DMPK and CNBP gene transcripts, reducing

toxic RNA foci and restoring splicing. Their FDA approval in 2022 marked the first disease-

modifying treatment for DM1. Gene editing approaches employ CRISPR-Cas9 to directly

excise expanded trinucleotide repeats. Identifying other therapeutic targets and biomarkers

Symptom-oriented care requires coordinated efforts between neurologists, cardiologists,

ophthalmologists, endocrinologists and others. New therapeutics offer more optimism for

future functional stabilization and quality of life gains in living with this complex

multisystem genetic disorder.

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder characterized by

myotonia and muscle weakness. It represents the most common adult-onset muscular

dystrophy, with two clinical subtypes—Type 1 DM (DM1) caused by CTG trinucleotide

repeat expansion in the DMPK gene, and Type 2 DM (DM2) due to CCTG repeats in CNBP.

Beyond myotonia and myopathy, DM impacts multiple organs through RNA toxicity and

dysfunction of alternative splicing regulatory proteins. This discussion explores the genetic

neuromuscular condition.