Ultrastructural studies on the neuromuscular junctions of Becker's muscular dystrophy.

Ultrastructural studies on muscle biopsies from three patients with Becker's muscular dystrophy showed that the i.m. nerves presented loss or disarrangement of the neurofilaments and an increased number of glycogen granules and/or myelin figures not infrequently in the myelinated and unmyelinated nerve fibers. The neuromuscular junctions showed markedly widened sole-plate areas, and several terminal axons frequently abutted and formed neuromuscular junctions on the same fiber. The secondary synaptic clefts were markedly decreased in number and short in length in type I fibers but not in type II fibers. Most terminal axons showed no degenerative changes. Therefore, the participation of a neural factor might be suggested as the cause of Becker's muscular dystrophy, although it does not mean denervation in the conventional sense of an axonal degeneration.