Atypical nemaline myopathy with temporomandibular ankylosis.

A young girl who initially presented with jaw hypomobility at age 4 years subsequently developed signs of a slowly progressive myopathy. Rods were found in all sampled muscles, and were associated with fibrous contractures in the temporomandibular joint muscles. Rods in fibers undergoing necrosis displayed a pattern of degradation that was almost identical to the pattern induced by calcium-activated neutral protease in vitro. It appears that this patient had nemaline myopathy, atypical in both clinical presentation and pathologic lesions.