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Myotonic Dystrophy — RACP Adult Medicine MCQ

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ModerateNeurologyMyotonic DystrophyRACP Adult Medicine

A 55-year-old man presents with progressive muscle stiffness and dysphagia. He has difficulty releasing his grip after handshake. EMG shows myotonic discharges. Genetic testing confirms CTG trinucleotide repeat expansion in the DMPK gene. What cardiac complication must be screened for?

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Correct answer: D — Conduction abnormalities (heart block)

Myotonic dystrophy type 1 (DM1) is associated with progressive cardiac conduction disease, including first-degree heart block, bundle branch block, and complete heart block, which can cause sudden cardiac death. Annual ECG and consideration of Holter monitoring or electrophysiology studies is recommended. Pacemaker or ICD may be required. Other systemic features include cataracts, diabetes, hypogonadism, and respiratory muscle weakness.

Reference: eTG – 2025 – Neurology; AAN – 2022 – Myotonic Dystrophy Guideline