VASCULAR INVOLVEMENT IN BENIGN INFANTILE MITOCHONDRIAL MYOPATHY CAUSED BY REVERSIBLE CYTOCHROME-C-OXIDASE DEFICIENCY

A 1-month-old Japanese girl had profound generalized weakness, hypoton ia, and severe lactic acidosis, The infant improved gradually: she hel d her head at 9 months, learned to walk by 15 months, At the first mus cle biopsy at 11 weeks of age, the specimen was characterized by numer ous ragged-red fibers and decreased enzyme activity on cytochrome c ox idase (COX) staining, Electron microscopic findings were characterized by the presence of excessive abnormal mitochondria not only in skelet al muscle fibers but also in blood vessels, Vascular abnormalities con sisted of an increased number of enlarged mitochondria in endothelial and smooth muscle cells of small arteries, Biochemical analysis showed an isolated defect of COX activity, which was only 16% of the mean co ntrol level, At the second biopsy at 44 months of age, the COX activit y had increased to normal in the entire specimen, On electron microsco py, the abnormal mitochondria present on the first biopsy specimen had disappeared both in muscle fibers and blood vessels; nearly all mitoc hondria were morphologically normal at the second biopsy. Now at 5 yea rs of age she can run and does not show muscle weakness, We report rev ersibility of abnormal mitochondria with age not only in skeletal musc le fibers but also in blood vessels in a patient, who had reversible C OX deficiency with a benign clinical course.