Cytochrome oxidase deficiency in Alzheimer's disease.

Alzheimer's disease (AD) is a degenerative neurologic disorder that may be familial but is usually sporadic and not easily analyzable in terms of conventional Mendelian genetics. The mitochondrial electron transport chain contains 13 proteins that are encoded by mitochondrial genes rather than nuclear (chromosomal) genes. Disorders resulting from heteroplasmic mutations of mitochondrial genes may appear to be sporadic rather than familial. We evaluated electron transport chain activity in platelet mitochondria prepared from patients with AD and found a specific defect in cytochrome oxidase in five of six patients studied. The mitochondrial genome may play a role in the pathogenesis of AD.