We report a 22-year-old very thin man, who showed various symptoms and signs of oculoskeletal muscle weakness, episodes of myalgia, prolonged diarrhea, severe myopia, perceptive deafness, electrocardiographic and electroencephalographic abnormalities, and endocrinological abnormality. The onset was at about 3 months of age and a positive family history was strongly suggested. The light-microscopic, histochemical and electron-microscopic findings showed abnormal mitochondria not only in the skeletal muscle, but also in liver cells. From the clinical as well as morphological points of view, this case was suspected to be one of congenital oculoskeletal myopathy probably due to an unidentified systemic metabolic disorder.