X-linked vacuolated myopathy: membrane attack complex deposition on muscle fiber membranes with calcium accumulation on sarcolemma.

Cytochemical localization of calcium on muscle fibers from patients with X-linked vacuolated myopathy demonstrated strong sarcolemmal or vacuolar calcium deposits in histologically abnormal muscle fibers. All membrane attack complex-positive fibers demonstrated such calcium accumulation. Total content of calcium was significantly elevated in muscles from patients with X-linked vacuolated myopathy compared to control muscles. Taken together, these results suggest that calcium accumulation on sarcolemma could be probably secondary to membrane attack complex deposition on the cell surface.