Spuriously high CK-MB isoenzyme activity mimicking acute myocardial infarction in a patient with adenocarcinoma of the rectum.

A 58-year-old Chinese male presented with precordial distress and was found to have elevated creatine kinase (CK)-myocardial bound (MB) (determined by the Kodak Ektachem Clinical Chemistry Slide method) activity and an abnormal electrocardiogram. Eventually, the patient was diagnosed with an annular ulcerative tumor 10 cm above the anal orifice. The tumor was an adenocarcinoma of the rectum and was immunoreactive for CK-BB (brain type). CK isoenzyme electrophoresis disclosed both BB and MM (muscle type) bands. We concluded that the level of CK-MB determined using the Kodak Ektachem Clinical Chemistry Slide method was spuriously elevated in our patient with adenocarcinoma of the rectum, without evidence of myocardial injury. Institutions using the Kodak Ektachem Clinical Chemistry Slide system for CK should be aware of this possibility.