Muscle Creatine Phosphokinase in Primary Myopathies ∗

Abstract

Summary and Conclusions

In terms of wet weight of the biopsy sample, muscle creatine phosphokinase (CPK) may be decreased in skeletal muscle from patients with pseudohypertrophic muscular dystrophy (PHMD); however, despite such decreases, CPK activity in terms of nitrogen in the supernate of the assay sample remains within the normal range. Hence the low values, when present, result in all probability from the increased fat content of muscle. Muscle CPK per unit of wet weight or in relation to supernate nitrogen in the assay sample was not low in a limited number of observations in limb girdle and facio-scapulo-humeral muscular dystrophy; this also appeared to be so in the few examples of myotonia dystrophica and of polymyositis examined by the above technics. The addition of a sulfhydryl compound to the assay mixture did not produce a statistically significant difference in the CPK activity of skeletal muscle obtained at biopsy which was refrigerated and assayed promptly. Quantitative differences in the reports of assays of muscle CPK activity by methods in current use are cited.