Oculoskeletal myopathy with abnormal mitochondria.

A clinical, electrophysiological and pathological review of 14 patients having oculoskeletal myopathy with abnormal mitochondria was undertaken. These patients present with ophthalmoplegia, and mild skeletal muscle weakness. The clinical course is slowly progressive. Electromyographic examination shows myopathic changes. Serum enzymes are normal. The diagnosis is confirmed by skeletal muscle biopsy which shows abnormal mitochondria, including crystalloid inclusions on electron microscopy. These patients form a distinct clinical group in which the risk of sudden cardiac death is much less than it is in the Kearns-Sayre syndrome.