Muscle histology in Becker muscular dystrophy.

Twenty patients with Becker muscular dystrophy (BMD), confirmed by dystrophin tests, were studied histologically. There were several morphological differences between younger (less than or equal to 15-year-old) and older (greater than 15-year-old) patients. In the younger patients, active muscle fiber necrosis followed by a regenerating process was conspicuous. In the older patients, the active degenerative changes appeared less prominent and, instead, more chronic myopathic changes such as moth-eaten fibers, fiber splitting, and hypertrophic fibers were evident. These age-dependent differences in the pathology of BMD were irrespective of the duration of clinical symptoms, i.e., BMD patients of a similar age showed a similar morphological feature regardless of age at onset. Although the presence of mild fiber type grouping and some small angulated atrophic fibers suggested a certain degree of neurogenic involvement, none of biopsies showed significant grouped atrophy as seen in neuropathic disorders. There was no correlation between the histological changes and the specific dystrophin abnormality.