Myotonic Muscular Dystrophy

Myotonic muscular dystrophy is a common multi-system disorder that affects the skeletal muscles (the muscles that move the limbs and trunk), as well as smooth muscles (the muscles that control the digestive system) and cardiac muscles of the heart. Symptoms of myotonic dystrophy might include difficulty releasing one's grip (myotonia), weakness of muscles in the hands and feet, difficulty swallowing, abnormal movements of the gut muscles, and abnormal heart rhythms. Non-muscle symptoms may also include learning difficulties, daytime sleepiness, infertility, endocrine abnormalities, and early cataracts. There are two known forms of this disease -- Myotonic Dystrophy Type 1 and Myotonic Dystrophy Type 2. Both forms are caused by abnormal expansions of repeated areas of specific genes. In Myotonic Dystrophy Type 1, the repeat expansion increases with each generation, frequently leading to earlier onset and increased severity of symptoms with each affected generation. Myotonic Dystrophy Type 1, therefore, frequently affects children more severely in families with this disorder.

Diagnosis:

The diagnosis of Myotonic Dystrophy is based on the clinical assessment, including a family history, physical examination and supporting laboratory studies. These studies may include blood work, electrodiagnostic testing (EMG), and occasionally, muscle biopsy. A definitive diagnosis is usually possible through a blood test to detect the specific genetic defect responsible for Myotonic Dystrophy type 1 or type 2. Our genetic counselor will carefully review the history of disease with each patient, discuss the principles of inheritance and help weigh risks and benefits of genetic testing in the patient and, if appropriate, in various family members.

Treatment:

Treatment of Myotonic Dystrophy involves a multidisciplinary team. A neurologist oversees the various needs of the patient and directs care. The neurologist may recommend that myotonia, the inability to relax muscles, be treated with a drug such as mexiletine. An ECG, and often an echocardiogram, will be performed to assess the heart's rhythm and function. A test of lung function will also be performed. Depending on the neurologist's findings and results of these tests, consultation with other specialists who also have expertise in myotonic dystrophy -- such as cardiologists, pulmonologists, and ophthalmologists -- will be recommended for additional treatment. Specialists in rehabilitation medicine are present in the clinic to meet with patients and provide individualized exercise and stretching programs for the treatment of weakness and contractures. On the same day, the patient will be evaluated for the need for splints and orthotics to help with hand or foot function. Myotonic dystrophy is a complex disorder that affects many organ systems throughout the body. Most people with myotonic dystrophy can lead full, successful lives. This requires the involvement of health care professionals with experience and dedication to the disease as are found at Kennedy Krieger.