E Theodoraki et al. Inflamm Bowel Dis 2018; 24: 1266-71. This study with 82 infliximab-treated patients with a mean age of 44 years found elevated CK levels (>180 U/L) in 30.5%, compared with 11% of control group (IBD patients not receiving biologic therapy). The median CK value in the IFX group was 123.5 U/L compared with 81 U/L in the control group (P<0.0001). All patients had at least 3 CK measurements. The authors recommend: “Based on our results, we recommend monitoring CK levels and clinical symptoms of muscle pain and weakness in IBD patients on IFX treatment.”
In the associated commentary (pg 1272-3), the authors note that CK is found in mitochondria, mainly in cardiac muscle, brain, skeletal muscle and other visceral tissues. The 2 subunits may create 3 isoenzymes: CK-MB (myocardium), CK-MM (skeletal muscle), and CK-BB (neurons). CK can be elevated in health and disease but “in the absence of symptoms, usually do not require any further investigations.” In a small number of individuals, elevated CK can be due to macro-CK (macrocretin) due to measurement difficulties with macroenzymes.
My take: This study suggests that elevated CK levels are common in adults receiving IFX and to avoid overreaction.