CK-BB is elevated in which condition according to the material?

• A. Macro-CK / IgG bound CK1
• B. CK-MM
• C. CK-MV
• D. CK-BB

Answer: (A)

Macroenzymes explain why CK-BB can appear elevated even without brain injury. When CK binds to immunoglobulins, it forms a large complex called macro-CK. This IgG-bound CK1 is detected as increased CK activity in serum, and the CK present in this macroenzyme is predominantly the CK-BB form. So the apparent rise in CK-BB arises from the macro-CK/IgG-bound CK1 complex rather than from release of CK-BB from brain tissue. The other usual tissue-derived isoforms (CK-MM from skeletal muscle or CK-MB from heart) reflect actual tissue injury, not this macroenzyme phenomenon, and there isn’t a standard CK-MV isoform to explain the finding.