Macro-creatine kinase syndrome as an underdiagnosed cause of ck-mb increase in the absence of myocardial infarction: two case reports.

When assessing an acute coronary syndrome (ACS) by means of high serum levels of creatine kinase (CK) and its MB fraction (CK-MB), one must keep in mind that there are several other causes for an increase of these markers, such as myocarditis, pericarditis, heart failure, severe aortic stenosis, stroke, renal failure, malignant hyperthermia, Reye syndrome, polymyositis, and borreliosis (1). Also, there are cases when CK-MB is falsely increased due to certain abnormalities that occur in the CK isoenzymes. One such example is the formation of the so-called macro-creatine kinase complexes (macro-CK) that give a false increase of the CK-MB fraction. We report two clinical cases where macro-CK was the cause of apparent increase in serum CK and CK-MB: in a 79-year old male with a history of coronary disease and a 82-year old female with permanent atrial fibrillation.