The spectrum of mild X-linked recessive muscular dystrophy.

We present 19 patients from 12 families with mild (Becker) X-linked recessive dystrophy and compare them with previously described cases. Features in common in the majority of patients include onset after the age of 7 years, walking beyond the age of 20 to 30 years, mild hypertrophy of the calves, mild joint contractures, and high arched feet. Pshychometric tests, EEGs, and ECGs were usually normal. Muscle biopsy specimens showed a combination of features, some more characteristic of severe (Duchenne) X-linked dystrophy and others more commonly seen in limb girdle dystrophy. Although there was some variation in the severity between different families, within any one kindred, the clinical picture was quite similar.