What are the symptoms of myotonic dystrophy?

From the Guidelines

Myotonic dystrophy symptoms include muscle weakness and wasting, myotonia, cataracts, cardiac conduction abnormalities, and endocrine disturbances, among others, as reported in a scientific statement from the American Heart Association 1. The symptoms of myotonic dystrophy can be divided into several categories, including:

• Muscular symptoms: muscle weakness and wasting that typically begins in the face, neck, and limbs, along with the characteristic myotonia (delayed muscle relaxation after contraction) 1.
• Ocular symptoms: cataracts are a common feature of myotonic dystrophy, and patients may also experience drooping eyelids (ptosis) 1.
• Cardiac symptoms: cardiac conduction abnormalities, including atrioventricular or intraventricular conduction defects and tachyarrhythmias, are present in approximately 80% of patients with myotonic dystrophy type 1 (DM1) 1.
• Endocrine symptoms: endocrine disturbances, such as insulin resistance and testicular atrophy in men, may occur in patients with myotonic dystrophy 1.
• Other symptoms: patients may also experience respiratory weakness, excessive daytime sleepiness, gastrointestinal issues, cognitive impairment, and behavioral changes 1. The severity and progression of symptoms vary widely between individuals, even within the same family, due to the phenomenon of anticipation where symptoms can worsen in successive generations, particularly in DM1 1.

From the Research

Symptoms of Myotonic Dystrophy

• Progressive muscular decline 2
• Neurologic abnormalities 2
• Cardiac disease, including:
  • Atrial arrhythmia 2
  • Left ventricular systolic dysfunction 2
  • High-degree atrioventricular block 2
  • Ventricular arrhythmia 2
• Myotonia, which can interfere with daily activities such as walking or climbing stairs 3
• Decreased dexterity 4
• Gait instability 4
• Difficulty with speech/swallowing 4
• Muscle pain 4

Effects of Myotonic Dystrophy on Daily Life

• Myotonia can affect daily activities, making it difficult for patients to perform tasks that require muscle relaxation 3, 4
• Cardiac manifestations can lead to significant morbidity and mortality, making early diagnosis and prevention crucial 2

Treatment and Management

• Mexiletine, a class 1b antiarrhythmic sodium antagonist, has been shown to be effective in reducing myotonia in patients with myotonic dystrophy 3, 5, 4, 6
• Cardiac assessments are necessary prior to initiation and throughout treatment with mexiletine due to potential proarrhythmic effects 5, 6