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.