Atypical serum creatine kinase isoenzyme pattern caused by complexing of creatine kinase-BB with immunoglobulins G and A1),2).

12 cases are described, which show high serum creatine kinase-BB levels, as well as atypical creatine kinase activity band located between normally migrating creatine kinase-MM and creatine kinase-MB. It is shown that the altered properties of the serum creatine kinase-BB, namely its molecular size, heat resistance, electrophoretic mobility, but not its immunological behavior, are caused by complexing with kappa-chains of immunoglobulins G or A. The complex occurring in vivo could also be produced in vitro by using purified patients' IgG and human creatine kinase-BB.