A term applied to a group of developmental changes occurring in the muscles, independently of the nervous system (see MUSCLES, DISORDERS OF). The best-known form is progressive muscular dystrophy, a group of hereditary disorders characterised by symmetrical wasting and weakness, with no sensory loss. There are three types: Duchenne (usually occurring in boys within the first three years of life); limb girdle (occurring in either sex in the second or third decade); and facio-scapulo-humeral (either sex, any age). The three types have different prognoses, but may lead to severe disability and premature death, often from respiratory failure. The third type progresses very slowly, however, and is compatible with a long life.

Diagnosis may be confirmed by ELECTROMYOGRAPHY (EMG) or muscle biopsy. Although genetic research is pointing to possible treatment or prevention, at present no effective treatment is known, and deterioration may occur with excessive confinement to bed. Physio-therapeutic and orthopaedic measures may be necessary to counteract deformities and contractures, and may help in coping with some disabilities.