Detection of subclinical and carrier states in Duchenne muscular dystrophy

Three methods of study, consisting of determinations of serum creatine phosphokinase and aldolase, electromyography, and muscle biopsy, were utilized to study clinically uninvolved members of nine families containing one or more known cases of muscular dystrophy. The combined use of these methods of study allowed detection not only of advanced myopathic changes, but also of minimal abnormalities considered characteristic of the heterozygous state. The graded findings formed a useful basis for a rational classification of abnormalities to denote “preclinical”, “carrier” and “presumptive carrier” states. In addition, results provided further indirect evidence that X-chromosome mosaicism may be operative in the inheritance of the Duchenne type of muscular dystrophy.