Muscle hypertrophy with neuropathy.

A patient with insidious onset of weakness, muscle atrophy and true hypertrophy, and sustained spasms is described. The spasms, initially mistaken to be myotonic, were shown electromyographically to result from sustained activity of the muscle fibres. An additional clinical manifestation verified myographically, was impaired reciprocal inhibition. Also, the patient had thick peripheral nerves and very slow motor (but normal sensory) nerve conduction. Histologic examination of sural nerve biopsy revealed large vacuoles within Schwann cells containing unidentified material, as well as onion-bulb formations. The possibility of a metabolic error resulting in storage of an abnormal material within Schwann cells is assumed.