Peripheral source of MB band of creatine kinase in alcoholic rhabdomyolysis. Nonspecificity of MB isoenzyme for myocardial injury in undiluted serum samples.

The MG isoenzyme of creatine kinase (CK MB) was strongly positive in the serum of a patient with alcoholic rhabdomyolysis, and it remained detectable by a standard qualitative assay over a two-year period without clinical or laboratory evidence of myocardial disease. MB isoenzyme was also demonstrated in a homogenate of skeletal muscle. Isoenzyme determinations in serum and tissue were repeated after dilution of toal CK activity to the range optimal for the assay (300 IU/L). Such dilution before isoenzyme separation rendered these samples negative for CK MB. The MB isoenzyme may be detectable in serum from peripheral sources in the presence of high total CK concentrations.