Chronic progressive external ophthalmoplegia (CPEO): clinical, morphologic, and biochemical studies.

We studied skeletal muscles from eight chronic progressive external ophthalmoplegia patients with ragged-red fibers (group A), five CPEO patients without ragged-red fibers (group B), and five controls. The EM morphometric fraction of structurally abnormal mitochondria was increased in group A, and there was a similarly increased fraction of normal-appearing mitochondria in group B. State 3 respiration and uncoupled respiration were severely decreased in both groups. The morphometric mitochondrial fraction and respiratory functions were inversely related in all three groups. The cytochrome content in group A was normal; cytochromes b and cc1 were decreased in group B. These studies point to a central role of mitochondrial dysfunction in all types of CPEO, but the basic abnormalities remain to be elucidated.