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December 19, 1986

Elevated Atypical Creatine Kinases

JAMA. 1986;256(23):3216. doi:10.1001/jama.1986.03380230039014

To the Editor.—  We read with interest the CASE REPORT of a patient with metastatic adenocarcinoma of the lung and elevated serum CK isoenzyme with an electrophoretic pattern consistent with the MB fraction.1We have reported a similar case of a patient with metastatic oat cell carcinoma who had persistent elevation of the serum CK with isoenzyme fractionation showing CK-MB in the range of 47% to 53% and CK-BB in the range of 11% to 23%.2 At postmortem examination, there was no evidence of myocardial injury. Of interest, however, was that measurement of CK isoenzymes in the patient's tumor tissue showed 46% MB, 44% BB, and only 9% MM, while the myocardium showed 93% MM and 7% MB fraction and skeletal muscle 97% MM and only 3% MB fraction.Although the nature and mechanisms of production of these CK isoenzymes by malignant tissue remain unclear, we demonstrated that