1. the isoenzymes of creatine kinase. Creatine kinase is a dimer with M (muscle) and/or B (brain) subunits; it exists in three isoenzyme forms: CK-MM, the predominant form, found primarily in skeletal muscle; CK-MB, found in cardiac muscle, tongue, diaphragm, and in small amounts in skeletal muscle; and CK-BB found in the brain, smooth muscle, thyroid, lungs, and prostate. Elevations detected by electrophoresis or other methodologies can be used to help in the differential diagnosis of a variety of disease states, with CK-MB elevations as an important marker following myocardial infarctions, elevations in CK-MM an indicator of muscle disease, and increases in CK-BB an occasional finding following brain infarcts, bowel infarcts, or in the presence of certain malignancies.
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