Mitochondrial myopathy and sideroblastic anemia.

We report four new cases of mitochondrial myopathy and sideroblastic anemia (MSA). Hallmark features of MSA include progressive exercise intolerance during childhood, onset of sideroblastic anemia around adolescence, basal lactic acidemia, and mitochondrial myopathy. Autosomal recessive inheritance of MSA in the family we describe is assumed due to the presence of two affected sibling pairs, unaffected parents, an unaffected sibling, and parental consanguinity. The nuclear families we describe are paternally related and originate from the same Iranian city as a family with MSA described by [Inbal et al., 1995]. These families provide an opportunity to clarify the molecular basis of tissue specific expression of mitochondrial disorders.