Mitochondrial myopathy.

Six clinically affected and 18 asymptomatic members of a six-generation family were investigated clinically, by estimation of serum CK levels, and in some cases by quantitative electromyographic techniques and muscle biopsy. It was concluded that the myopathy was probably inherited as an autosomal dominant trait with variable expression and incomplete penetrance although the possibility of mitochondrial inheritance could not be excluded in view of the almost exclusive transmission through the female line. Eight members of the family with myopathy also had diabetes mellitus, and 2 of these also had cerebellar ataxia. It is suggested that the myopathy, the cerebellar disorder and the diabetes may all be manifestations of the same underlying metabolic defect.