Overview
Myotonic dystrophy (DM) is an autosomal dominant, multisystem disorder characterized by myotonia and progressive muscle weakness. Both myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) affect skeletal and smooth muscle and may involve the cardiac, respiratory, endocrine, ocular, gastrointestinal, and central nervous systems. Clinical presentation and progression are highly variable, even within families.
DM1:
- Clinical overview of myotonic dystrophy type 1 (DM1): https://www.ncbi.nlm.nih.gov/books/NBK1165/
DM2:
- Clinical overview of myotonic dystrophy type 2 (DM2): https://www.ncbi.nlm.nih.gov/books/NBK1466/
Anesthesia and sedation
Individuals with DM1 and DM2 have increased sensitivity to sedatives, analgesics, and anesthetic agents. Risks are highest in the post-anesthesia period and include respiratory failure, aspiration, and cardiac complications. Advanced planning and postoperative monitoring are critical.
Anesthetic management:
Cardiac complications
Cardiac conduction abnormalities and arrhythmias are a major cause of morbidity and mortality in DM1 and are also reported in DM2. Cardiac involvement may occur even when neuromuscular symptoms are mild, making routine surveillance essential.
Clinical guidance:
- MDF Consensus-based Care Recommendations for Adults with DM1
- MDF Consensus-based Care Recommendations for Adults with DM2
- MDF Cardiology Consensus Recommendations for Adults with DM1
Respiratory complications
Chronic respiratory impairment is a leading contributor to morbidity and mortality in DM1 and may also affect individuals with DM2, particularly with advanced disease or comorbidities . Symptoms may be subtle and not evident without proactive assessment.
Clinical guidance:
Gastrointestinal complications
Gastrointestinal (GI) involvement is common in both DM1 and DM2 due to smooth muscle dysfunction. GI manifestations are often unrecognized and may include dysphagia, esophageal dysmotility, delayed gastric emptying, constipation, diarrhea, abdominal pain, and gallbladder dysfunction. GI symptoms may contribute to malnutrition, aspiration risk, and reduced quality of life.
Cognitive and neurobehavioral features
Cognitive impairment, executive dysfunction, attention difficulties, excessive daytime sleepiness, apathy, and anosognosia are well documented in DM1 and are also reported in DM2. These features can directly affect symptom recognition, health literacy, adherence to treatment plans, and engagement in shared decision-making.
Actively discussing cognitive and neurobehavioral features with patients and families is critical. When these issues are not addressed, they may be misinterpreted as nonadherence, lack of motivation, or psychiatric illness, leading to gaps in care and increased caregiver burden. Normalizing cognitive and behavioral features as part of the disease process supports earlier identification, appropriate referrals, and more effective care planning.
Communicating with patients and families
Cognitive and behavioral features are part of the disease process in DM1 and DM2. Providers are encouraged to use clear, concrete language, verify understanding, allow additional time for discussion, and involve caregivers or family members when appropriate. These strategies support shared decision-making and adherence to care plans.
Clinical framework:
Supportive services
Supportive services may be integrated as needed to address functional, daily living, and communication needs over time.
Additional discipline-specific resources:
- MDF Role of Physical Therapy in DM
- MDF Occupational Therapy Guidelines
- MDF Pregnancy Care Guidelines
Genetic diagnosis and testing
A panel that includes testing for the DMPK CTG repeat expansion and other disorders of interest as part of the differential diagnosis may be considered to identify the genetic cause of the condition as quickly as possible.
Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests. In general, a panel that includes analysis for nucleotide repeats and other non-sequencing-based tests (e.g., SMN1 copy number analysis, methylation testing for Prader-Willi syndrome, UPD14 analysis) is recommended. Although the CTG repeat expansion will not be detected by a multigene short-read sequencing panel, this testing may be appropriate for some conditions in the differential diagnosis.
Gene specific test:
Gene specific tests for DMPK and CNBP only detect expanded CTG repeats in the DMPK or CNBP genes respectively using specialized genetic testing, typically from a blood or saliva sample. The primary tests are PCR (Polymerase Chain Reaction) for identifying expansion size, and Southern Blot or Triplet Repeat-Primed PCR to confirm large expansions
Testing methodologies and provider landscapes are rapidly changing and evolving. It is highly recommended to utilize genetic counselors for guidance regarding patient education, appropriate test selection and orders, interpretations, and communicating results with providers, patients, and families.
