Interleukin-6 and soluble interleukin-2 receptor alpha-markers of inflammation in patients with psoriatic arthritis?

OBJECTIVE To evaluate a possible systemic effect of joint inflammation in contrast to skin disease only, by measuring IL-6 and IL-2sRalpha. METHODS Two hundred and nineteen patients (111 male / 108 female, age 50.4+/-14.5 yrs (mean+/-SD)) with psoriasis were clinically and laboratory examined. 134 patients had inflammatory joint manifestations defined as peripheral arthritis and/or axial disease, of whom 37 had measurable inflammation, defined as ESR >25 mm/h and/or CRP >15 mg/L. RESULTS Interleukin-6 was significantly higher in patients with joint disease and measurable inflammation ((median, Q1-Q3) 4.07, 0.92-14.60), and in patients without measured inflammation (1.22, 0.70-3.46), compared to patients with skin disease only (0.70, 0.70-1.73, p<0.001 and p=0.002 respectively). The difference between the two groups of patients with inflammatory joint manifestations was significant (p=0.001). The levels of IL-6 correlated with the actual number of joints affected with arthritis (p<0.001; rs=0.248), ESR (p<0.001; rs=0.459), CRP (p<0.001; rs=0.314) and IL-2sRalpha (p=0.002; rs=0.210). The levels of IL-2sRalpha. did not differ between the 3 groups. CONCLUSION In this study, IL-6 was significantly higher in patients with psoriasis and inflammatory joint disease with or without routine measurable inflammatory activity compared with patients having psoriasis of the skin. We found that patients with psoriasis and joint inflammation may have systemic effects that could be captured by serum measurements of IL-6. Soluble IL-2Ralpha was not a marker of inflammation in this study.