Muscle biopsy in the evaluation of patients with modestly elevated creatine kinase levels.

The utility of muscle biopsy in patients with modest elevations of serum creatine kinase (CK) level but normal neurological examinations and nondiagnostic electrodiagnostic studies is uncertain. We performed systematic, extensive studies on muscle biopsies of 20 such patients. A definitive diagnosis was arrived at in only 1 by histochemical studies, although 4 others demonstrated minor myopathic changes. Biochemical evaluation led to a diagnosis in an additional 5. Muscle biopsy is useful for evaluating such patients, but extensive studies of the muscle are necessary.