Benign infantile mitochondrial myopathy due to reversible cytochrome c oxidase deficiency.
A 2-week-old boy had profound generalized weakness, hypotonia, hyporeflexia, macroglossia, and severe lactic acidosis. The infant improved spontaneously: he held his head at 4 1/2 months, rolled over at 7 months, and walked by 16 months. At 33 months of age, he had mild proximal weakness. Macroglossia disappeared by age 4 months. Blood lactic acid declined steadily and was normal by 14 months of age. Histochemical and ultrastructural studies of muscle biopsy specimens obtained at 1 and 7 months of age showed excessive mitochondria, lipid, and glycogen; a third biopsy at age 36 months showed only atrophy of scattered fibers. Cytochrome c oxidase stain was positive in fewer than 5% of fibers in the first biopsy, in approximately 60% of fibers in the second biopsy, and in all fibers in the third biopsy. Biochemical analysis showed an isolated defect of cytochrome c oxidase activity, which was only 8% of the lowest control level in the first biopsy; the activity increased to 47% in the second biopsy and was higher than normal in the third. In contrast to that in the fatal infantile form of cytochrome c oxidase deficiency, the enzyme defect in this condition is reversible. The biochemical basis for this difference remains to be explained.
D000138:Acidosis / Q000201:enzymology; D001706:Biopsy; D002675:Child, Preschool; D030401:Cytochrome-c Oxidase Deficiency; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000097:blood; D050356:Lipid Metabolism; D008297:Male; D008854:Microscopy, Electron; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000648:ultrastructure; D009123:Muscle Hypotonia / Q000201:enzymology* / Q000473:pathology; D009132:Muscles / Q000201:enzymology / Q000473:pathology
D007773:Lactates; D006003:Glycogen