Serum Creatine Phosphokinase Isoenzyme (CPK2) in Myositis

Serum creatine phosphokinase (CPK) isoenzyme levels were studied in six cases: two with polymyositis, two with dermatomyositis, and two with viral myositis without neurological involvement. In all patients, agarose gel fractionation and fluorometric quantitation of serum CPK isoenzymes showed the presence of CPK2, although there was no evidence of myocardial infarction. Thus, CPK2is not exclusively found in myocardial infarction. The prolonged elevation of CPK2levels during periods of acute exacerbation of myositis in the reported cases is in contrast to the usual transient increases in myocardial infarction. Levels of serum lactate dehydrogenase (LDH), aspartate aminotransferase, and aldolase were invariably increased in these patients. The expected LDH5increase with myositis was not found. (JAMA230:1141-1144, 1974)