Macroenzyme creatine kinase in the era of modern laboratory medicine.

Among the conditions in which creatine kinase (CK)-MB activity is elevated in the absence of myocardial injury or infarction, macroenzyme (macro) CK merits special attention from clinicians. We present 2 cases, 1 with macro CK type 1 and the other with macro CK type 2, to stress the common clinical situations and diagnostic dilemma that clinicians encounter when evaluating patients with macro CK. Moreover, the rare conditions associated with macro CK, and the phenomenon of spuriously high CK-MB activity out of proportion to total CK, are discussed. The biochemical characteristics, clinical significance and potential implications of macro CK are reviewed within the scope of modern laboratory medicine.