Focal cytochrome c oxidase deficiency in the brain and dorsal root ganglia in a case with mitochondrial encephalomyopathy (tRNA(Ile) 4269 mutation): histochemical, immunohistochemical, and ultrastructural study.

This is the first report with histochemical and immunohistochemical techniques of an autopsy case with mitochondrial encephalomyopathy caused by the mitochondrial tRNA(Ile) (nt4269) A to G mutation showing focal cytochrome c oxidase (COX) deficiency of neuronal cells. The 18-year-old male patient had cardiomyopathy, hearing disability, mental retardation, and seizures. Muscle biopsy exhibited many ragged-red fibers and focal COX deficiency. A postmortem histochemical study on frozen sections of the cerebral cortex, cerebellum, brain stem, and dorsal root ganglia revealed a loss of COX activity in some neuronal cells. On immunohistochemical staining, COX was also defective in a mosaic pattern. Focal COX deficiency may cause variable neurological manifestations in mitochondrial encephalomyopathies.