A mitochondrial encephalomyopathy with specific deficiencies of two respiratory chain polypeptides and a circulating autoantibody to a mitochondrial matrix protein.

A 15-yr-old boy with mitochondrial encephalomyopathy and NADH CoQ reductase (Complex I) deficiency is presented. Immunoblotting demonstrated specific deficiencies of the 24 kDa FeS protein of Complex I and subunit II of Complex IV. The patient's serum contained an antibody to a specific mitochondrial matrix polypeptide of apparent Mr 41 kDa. The specific polypeptide deficiencies involve products of nuclear (24 kDa FeS protein) and mitochondrial (subunit II) genes and suggest some intergenomic regulation. The relevance of the circulating antibody to the pathogenesis of the patient's Complex I deficiency is discussed.