Progressive external ophthalmoplegia. Evidence for a generalised mitochondrial disease with a defect in pyruvate metabolism.

Muscle biopsies from four patients with chronic progressive external ophthalmoplegia and pigmentary retinopathy with symptoms and signs from other organs were studied by means of light and electron microscopy. Examination revealed a marked proliferation of abnormal mitochondria with a degeneration of both muscle and nerve tissue. Blood levels of lactate and pyruvate were measured and abnormal values of these metabolites were found in the three patients with the most pronounced ultrastructural changes. On the basis of these findings it is suggested that there is a biochemical defect in pyruvate-lactate metabolism which could be responsible for the marked proliferation of the abnormal mitochondria.