Introduction: Creatine kinase muscle/brain (CK-MB) is an isoenzyme frequently used for early diagnosis of acute myocardial infarction. This is particularly impor-tant when patients present with symptoms suggesting angina pectoris. However, several conditions may lower the specificity of CK-MB determination. False positive increase can be seen in patients with renal failure, asth-ma, malignancies, pulmonary embolism, chest trauma, skeletal and myocardial injury and other disorders.
Case presentation: We present the case of a 72 year old woman which was admitted for upper respirato-ry symptoms and chest pain. ECG showed trigeminal ventricular extrasystoles, no signs of acute coronary syndrome. Troponin was normal, but total CK and CK-MB were elevated. The reevaluation showed no cli-nical symptoms, but CK-MB elevation persisted, over-stepping total CK values. CK electrophoresis revealed Macro CK type 1. She was investigated for autoimmu-ne diseases, which were ruled out, by serum markers and musculoskeletal biopsy. Endoscopy and biopsy, to-gether with serum tumor markers, revealed no patho-logical findings. Thyroid hormones, kidney and liver function were normal. Coronary angiography was not performed. The patient had been followed up, but CK-MB elevation persisted with normal CK.
Case particularity: Persistent elevation of CK-MB in a patient can lead to misleading diagnosis and treat-ment. At a first glance, our patient seems to have high CK-MB levels due to myocardial damage in the con-text of coronary artery disease. This can be particularly important in areas where troponin cannot be assessed. A high CK/CK-MB ratio in an asymptomatic patient can be suggestive for the presence of macro CK. In our case, macro CK type 1 was successfully identified. It has been previously reported that it can appear in hypothy-roidism, autoimmune diseases, myositis, malignancies or cardiovascular disease. In our case, the necessary determinations were made to exclude the previously mentioned conditions and we did not found any cer-tain cause.
Conclusions: This case report provides challenging di-agnostic suppositions. It triggers a signal for taking into consideration that elevation of CK-MB can be due to other causes than myocardial injury and can be trou-blesome in treatment decision. Macro-CK complexes can give a false increase of the CK-MB fraction.