Serum creatine kinase activity in 200 patients was studied in order to check whether this determination might be of help in differential diagnosis between primary and secondary (neurogenic) myopathies.
Elevated CK values are found physiologically in children, pregnant women, and after exercise. In pathological states increased serum enzyme concentrations (probably the expression of a defect in cellular permeability) are constantly present in the Duchenne type of progressive muscular dystrophy. More variable values are encountered in other types of muscular dystrophy and in metabolic disorders like Refsum's syndrome, coproporphyria, and hypothyroidism. In states of necrosis or injury to muscle cells like in polymyositis, dermatomyositis, after burns or trauma, serum CK concentrations vary according partly to the amount of muscle mass involved. Enzyme concentrations can be markedly increased after tetany or epileptic seizures. Normal values or occasionally slightly increased values are found in neurogenic myopathies. High CK values in patients with muscular atrophies should permit the clinician to exclude the differential diagnostic group of neurogenic myopathies.
As a diagnostic tool CK proved to be more reliable than transaminases or lactic dehydrogenase because of its higher muscle specificity and a slightly greater sensitivity.