Endocrine aspects of mitochondrial cytopathy: marked phenotypic variation in two affected siblings.

Two siblings with 'mitochondrial myopathy', one of whom was found to have hypergonadotrophic hypogonadism whilst the other had normal endocrine function are reported. The inheritance suggests an autosomal recessive mode. The protean manifestations of the disorder are emphasized. Attention is drawn to the possible association of endocrine abnormalities in addition to the more widely recognized neuromuscular signs.