Persistent creatine kinase MB isoenzyme without cardiac disease.

Although the creatine kinase MB isoenzyme may be useful in the diagnosis of myocardial injury, it is also found in the sera of patients with a number of noncardiac diseases. It may also occur in apparently normal individuals, as described in this case report. Hence, the diagnosis of myocardial injury should never be based solely on the presence of creatine kinase MB isoenzyme in the serum, but should be supported by additional clinical and laboratory data.