Skeletal muscle pathology in chronic progressive external ophthalmoplegia with ragged-red fibers

Summary Histochemical investigations were carried out on skeletal muscle biopsies from ten patients with chronic progressive external ophthalmoplegia with ragged-red fibers (RRF). In addition to the RRF, mild myopathic change consisting of variation in size of both type 1 and 2 fibers was seen in all patients, as well as neuropathic change in eight. Scattered fibers with absent cytochromec oxidase (CCO) activity (focal deficiency) were seen in all patients. In serial sections, CCO deficiency did not always occupy the entire length of a fiber but was localized segmentally to regions measuring several hundred micrometers in lenghth, suggesting the heterogeneity of CCO activity even in the same fiber.This work was partially supported by a Grant-in-Aid for Scienctific Research on Priority Areas (No. 626/7523) from the Ministry of Education, Science and Culture of Japan.