MITOCHONDRIAL MYOPATHY WITH A DEFECT OF MITOCHONDRIAL-PROTEIN TRANSPORT

The clinical and biochemical heterogeneity of the mitochondrial myopathies is now well established.1,2 Recent work has focused on identifying the molecular basis of these disorders and has demonstrated specific deficiencies of nuclear-encoded polypeptides in some patients3,4 and deletions of mitochondrial DNA in others.5,6 Deficiencies of nuclear-encoded polypeptides may be due to reduced synthesis, increased degradation, or defective transport of protein precursors from cell cytosol to mitochondria. We describe a patient with a pure myopathy and evidence of a deficiency of respiratory-chain Complexes I to IV. Immunoblotting of muscle mitochondrial preparations showed specific deficiencies of both the iron-sulfur protein of Complex. © 1990, Massachusetts Medical Society. All rights reserved.