Myotonic Dystrophies

Myotonic dystrophy I is a multisystem disorder. A common manifestation is chronic progressive muscle weakness which tends to involve neck muscles, face, and distal and proximal limb areas. Myotonia of grip and percussion is present early in the disease and becomes less prominent as weakness ensues. Extra muscular manifestations are early cataracts and frontal balding, infertility, diabetes mellitus, sleep disturbances, and cardiac arrhythmias. The diagnosis is achieved by family survey, characteristic electrophysiological findings, and Triplet repeat studies using TP-PCR or southern blotting. Mexiletine and other membrane stabilizers can reduce myotonic symptoms and cardiac evaluation and therapy are important. Long-term quality of life is compromised in the sufferers of myotonic dystrophy. Myotonic dystrophy 2 is less common, has a different genetic makeup, presents with proximal weakness and myotonia, and extra muscular manifestations are not prominent.