Mitochondrial Myopathy, Sideroblastic Anemia, and Lactic Acidosis: An Autosomal Recessive Syndrome in Persian Jews Caused by a Mutation in the PUS1 Gene

We report the seventh case of autosomal recessive inherited mitochondrial myopathy, lactic acidosis, and sideroblastic anemia. The patient, a product of consanguineous Persian Jews, had the association of mental retardation, dysmorphic features, lactic acidosis, myopathy, and sideroblastic anemia. Muscle biopsy demonstrated low activity of complexes 1 and 4 of the respiratory chain. Electron microscopy revealed paracrystalline inclusions in most mitochondria. Southern blot of the mitochondrial DNA did not show any large-scale rearrangements. The patient was found to be homozygous for the 656C→T mutation in the pseudouridine synthase 1 gene ( PUS1). Mitochondrial myopathy, lactic acidosis, and sideroblastic anemia is an oxidative phosphorylation disorder causing sideroblastic anemia, myopathy, and, in some cases, mental retardation that is due to mutations in the nuclear-encoded PUS1 gene. This finding provides additional evidence that mitochondrial ribonucleic acid modification impacts the phenotypic expression of oxidative phosphorylation disorders. ( J Child Neurol 2005;20:449—452).