Endocardial fibroelastosis: possible X linked inheritance.

We report a pedigree in which six males died of cardiac failure within the first eight months of life. These males were related through healthy females, as with X linked recessive inheritance. There was no consanguinity. None of the affected boys had an anatomical cardiac abnormality. In two affected brothers, histological evidence for endomyocardial fibroelastosis was documented, and in one of these electron microscopy demonstrated abnormalities of the mitochondria as found in mitochondrial cytopathy. A review of published reports revealed five similar X linked pedigrees, and in two of these mitochondrial abnormalities were found. We suggest that these families may show an X linked recessive cardiomyopathy with mitochondrial abnormalities.