Myotonic dystrophy

Myotonic dystrophy (DM) is a type of muscular dystrophy, a group of genetic disorders that cause progressive muscle loss and weakness. In DM, muscles are often unable to relax after contraction. Other manifestations may include cataracts, intellectual disability and heart conduction problems. In men, there may be early balding and an inability to father children. While myotonic dystrophy can occur at any age, onset is typically in the 20s and 30s. Myotonic dystrophy is caused by a genetic mutation in one of two genes. Mutation of the DMPK gene causes myotonic dystrophy type 1 (DM1). Mutation of CNBP gene causes type 2 (DM2). DM is typically inherited, following an autosomal dominant inheritance pattern, and it generally worsens with each generation. A type of DM1 may be apparent at birth. DM2 is generally milder. Diagnosis is confirmed by genetic testing. There is no cure. Treatments may include braces or wheelchairs, pacemakers and non-invasive positive pressure ventilation. The medications mexiletine or carbamazepine can help relax muscles. Pain, if it occurs, may be treated with tricyclic antidepressants and nonsteroidal anti-inflammatory drugs (NSAIDs). Myotonic dystrophy affects about 1 in 2,100 people, a number that was long estimated to be much lower (often cited as 1 in 8,000), reflecting that not all patients have immediate symptoms and, once they do have symptoms, the long time it typically takes to get to the right diagnosis. It is the most common form of muscular dystrophy that begins in adulthood. It was first described in 1909, with the underlying cause of type 1 determined in 1992. DM causes muscle weakness, early onset of cataracts, and myotonia, which is delayed relaxation of muscles after contraction. Cataracts can be either a cortical cataract with a blue dot appearance, or a posterior subcapsular cataract. Other organs affected include the heart, lungs, gastrointestinal tract, skin, and brain. Insulin resistance can also occur. Signs and symptoms vary considerably by severity, unusual phenotype, and form (DM1/DM2).

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Related concepts (5)

Myotonic dystrophy

Electromyography

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement.

Muscular dystrophy

Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare neuromuscular diseases that cause progressive weakness and breakdown of skeletal muscles over time. The disorders differ as to which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin. Some types are also associated with problems in other organs. Over 30 different disorders are classified as muscular dystrophies.