Diagnostic problem caused by an atypical creatine kinase isoenzyme in a patient with myocardial infarction

This report describes the diagnostic problem caused by an atypical immunoglobulin-bound creatine kinase isoenzyme in a patient who had a myocardial infarction. In the presence of this atypical isoenzyme, creatine kinase isoenzyme electrophoresis was of no help in determining whether myocardial infarction had occurred. A diagnosis of myocardial infarction was confirmed by carrying out lactate dehydrogenase isoenzyme electrophoresis and finding the characteristic increase in LD1/LD2 ratio and by following the total creatine kinase, aspartate aminotransferase and lactate dehydrogenase activities over a 5-day period. Further investigations were carried out which characterized the atypical isoenzyme as an uncommon type: creatine kinase-BB bound to immunoglobulin A lambda.