MYOPATHY, LACTIC-ACIDOSIS, AND SIDEROBLASTIC ANEMIA - A NEW SYNDROME

We describe 2 sibs (brother and sister) with myopathy, sideroblastic a nemia, lactic acidosis, mental retardation, microcephaly, high palate, high philtrum, distichiasis, and micrognathia. Very low levels of cyt ochromes a, b, and c were detected in the patients' muscle mitochondri a. Deposition of iron within the mitochondria of bone marrow erythrobl asts was observed on electron microscopy. Irregular and enlarged mitoc hondria with paracrystalline inclusions were also seen on electron mic roscopy of the patients' muscle specimen. Examination of DNA from the affected sibs showed no deletions in the mitochondrial DNA nor the mut ations identified in the syndromes of mitochondrial myopathy, encephal opathy, lactic acidosis, and strokelike episodes (MELAS) or myoclonus, and epilepsy associated with rugged-red fibers (MERRF). Since the par ents were first cousins and 2 of 6 sibs (male and female) were affecte d, we suggest that the syndrome expressed by our patients represents a previously unknown autosomal recessive disorder that includes mitocho ndrial myopathy, lactic acidosis, and sideroblastic anemia. (C) 1995 W iley-Liss, Inc.