Abnormal myomuscular junctions and AChE in a congenital neuromuscular disease.

We studied a patient with a congenital neuromuscular disease clinically characterized by ophthalmoplegia, slight limb muscle weakness, and normal electromyography. In the muscle biopsy, there were frequent examples of interdigitation of areas of muscle and extracellular spaces giving a fragmented appearance to muscle fibers. These structures resemble myomuscular junctions; acetylcholinesterase activity was present in the vicinity of these structures and on the muscle cell surface.