myotonic muscular dystrophy n : a severe form of muscular dystrophy marked by generalized weakness and muscular wasting that affects the face and feet and hands and neck; difficult speech and difficulty with the hands that spreads to the arms and shoulders and legs and hips; the onset can be any time from birth to middle age and the progression is slow; inheritance is autosomal dominant [syn: {myotonic dystrophy}, {myotonia atrophica}, {Steinert's disease}]