Myotonic ystrophy (DM) is a chronic, slowly progressing, highly variable inherited multisystemic disease that can manifest at any age from birth to old age. It is characterized by wasting of the muscles (muscular dystrophy), posterior subcapsular iridescent cataracts (opacity of the lens of the eyes), heart conduction defects, endocrine changes and myotonia (difficulty relaxing a muscle). Most notably, the highly variable age of onset decreases with successive generations. Thus the disease shows at an earlier age in successive generations, a phenomenon termed anticipation. There are two classifications of DM, each having different associated symptoms.