Source:http://linkedlifedata.com/resource/umls/id/C0553604
MSH: Diseases characterized by MYOTONIA, which may be inherited or acquired. Myotonia may be restricted to certain muscles (e.g., intrinsic hand muscles) or occur as a generalized condition. These disorders may be associated with abnormal muscle SODIUM CHANNEL and CHLORIDE CHANNELS. MYOTONIC DYSTROPHY and MYOTONIA CONGENITA represent two relatively common forms of this disorder. Proximal myotonic myopathy often presents with myotonia and muscle pain in early adulthood and later in life thigh muscle weakness and cataracts develop. (From Adams et al., Principles of Neurology, 6th ed, p1392),NCI: An inherited or acquired, localized or generalized disorder affecting the muscles. It may be associated with abnormalities in the chloride or sodium channels of the muscles. It is characterized by delayed muscle relaxation following stimulation or contraction. Representative examples include myotonia congenita and myotonic dystrophy.