Macro creatine kinase in a case of carnitine palmitoyltransferase deficiency

A stout man was admitted to the hospital with acute rhabdomyolysis associated with macro creatine kinase (macro-CK, EC 2.7.3.2). This anomaly of CK was detected by gel electrophoresis as an atypical band between CK-MB and CK-MM, classified according to Stein's criteria (Clin Chem 1982; 28:19-24) as type 1, and identified by immunofixation electrophoresis as containing CK isoenzymes MM and MB and immunoglobulin A. Muscle biopsy showed that the etiology of rhabdomyolysis in this case was deficiency of carnitine palmitoyltransferase (CPT, EC 2.3.1.21) in the muscle. We report the first observation of macro-CK in a case of CPT deficiency; its presence may result from recurrent rhabdomyolytic attacks owing to CPT deficiency, and may suggest underlying enzymic abnormality in muscle.