Evidence against the existence of a subclinical form of X-linked Duchenne muscular dystrophy

Abstract

Serum creatine kinase determinations have been carried out on 101 first-degree male relatives of patients with Duchenne and Becker types of X-linked muscular dystrophy and in an equal number of age-matched healthy male controls. The results suggest that an elevated creatine kinase level in a male relative (excluding preclinical cases) is unrelated to muscular dystrophy. There is no evidence that this represents either a subclinical form of X-linked Duchenne muscular dystrophy or the heterozygous state in autosomal recessive Duchenne muscular dystrophy. In the general population a proportion of normal healthy males have raised serum creatine kinase levels during everyday activity and a smaller proportion have raised levels even after bed rest. Possible explanations for these findings are discussed. It has been confirmed that the algebraic sum of the R and S waves in the first precordial lead of the electrocardiogram is abnormal in the majority of patients with the X-linked form but not in the autosomal recessive form of Duchenne muscular dystrophy.