Muscular dystrophy is a group of inherited diseases in which muscle fibers are abnormal and undergo atrophy. Most develop in early life or adolescence.
Duchenne dystrophy occurs in males although the genes for it are carried by females. It starts in early life and some swelling (pseudohypertrophy) of calf and other muscles may be seen. A similar disease can affect females. Other types, described by muscles mainly affected, include limb-girdle and facio-scapulo-humeral dystrophies. There are many diverse variants, largely due to structural or biochemical abnormalities in muscle fibers. Myotonic dystrophy occurs in older men, causing baldness, cataracts, testis abnormality, and a characteristic myotonus, in which contraction is involuntarily sustained.
Muscular dystrophies usually cause weakness and wasting of muscles, particularly of those close to and in the trunk; a waddling gait and exaggerated curvature of the lower spine are typical. The muscles of respiration may be affected, with resulting pneumonia and respiratory failure; cardiac muscle too may be affected. These two factors in particular may lead to early death in severe cases. Mechanical aids, including if necessary artificial respiration, may greatly improve well-being, mobility, and life span.