Benign infantile mitochondrial myopathy due to reversible cytochrome c oxidase deficiency

Ann Neurol. 1983 Aug;14(2):226-34. doi: 10.1002/ana.410140209.


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.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acidosis / enzymology
  • Biopsy
  • Child, Preschool
  • Cytochrome-c Oxidase Deficiency*
  • Glycogen / metabolism
  • Humans
  • Lactates / blood
  • Lipid Metabolism
  • Male
  • Microscopy, Electron
  • Mitochondria, Muscle / enzymology*
  • Mitochondria, Muscle / ultrastructure
  • Muscle Hypotonia / enzymology*
  • Muscle Hypotonia / pathology
  • Muscles / enzymology
  • Muscles / pathology


  • Lactates
  • Glycogen