MELAS with diffuse degeneration of the cerebral white matter: report of an autopsy case.

Up to now diffuse white matter demyelination of the cerebrum has been reported in only a few cases of mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). Here we document an autopsy case with this rare neuropathology. Most MELAS cases are diagnosed antemortem by A3243G transition of mitochondrial DNA. While cerebral damage including necrotic foci in the cerebral cortex are common findings in MELAS, prominent white matter involvement best characterizes this MELAS case. There were numerous necrotic foci, varying in size and chronological stage, in the cerebral white matter. In the areas of the white matter without necrotic foci, there was diffuse fibrillary gliosis with the loss of axons and oligodendrocytes. The gliosis was dominant in the deep white matter, sparing the U-fiber. The cerebral cortex showed diffuse cortical atrophy with few scattered necrotic foci. Distribution of the cerebral lesions does not coincide with the territory of blood supply. The vascular wall presented only slight to mild hyalinosis. We assumed a common pathogenesis to the cortical lesions and the white matter change. The pathogenesis of the present diffuse cerebral lesions may not be just secondary to circulatory disturbance but partly due to metabolic abnormality.