Macro Creatine Kinase (macro CK) in Clinical Practice

Abstract

Creatine kinase (CK) is an important enzyme involved in energy metabolism. CK is found in the cytosol and mitochondria of various tissues, mainly those with increased energy necessities as skeletal muscle, cardiac muscle and brain, but also in visceral tissues. CK is a dimeric molecule composed of two identical or different subunits, type M - muscular and type B - brain. The combination of M and B subunits leads to formation of three isozymes: CK - MM found mainly in the skeletal muscle, CK - BB found mainly in the brain and CK - MB found mainly in the cardiac muscle, but also in small quantities in the skeletal muscle. The serum increase of different isozymes of CK is a consequence of cell disruption in various clinical situations like physical training, rhabdomyolysis, myositis, muscular dystrophy, myocardial infarction and others, CK being an important biomarker for this diseases. Macro CK is a complex of CK and immunoglobulin (macro CK type 1) or a polymer of mitochondrial CK (macro CK type 2) that induces false and persistent elevation of CK levels that could mislead the clinician. We present a review of the literature concerning the appearance and clinical significance of macro CK.