An ocular myopathy with glycogen storage and abnormal mitochondria in muscle fibres. Histochemical and ultrastructural findings.

The case of a 66-year-old woman with progressive external ophthalmoplegia and involvement of the proximal muscles of the upper and lower limbs is described. EMG examinations show signs of myopathic involvement. Histochemical and biochemical studies exclude a primary defect in glycogenolysis. The authors stress the peculiarity of the histochemical findings, characterized by the rare associated appearance of both mitochondrial changes and glycogen accumulation in muscle fibres. The most prominent ultrastructural findings are evidence of increased glycogen, usually present in vesicles or in mitochondria, and changes in number, size and structure of mitochondria. Quantitative biochemical examination of muscle homogenates confirmed the increased content of glycogen in muscle fibres.