Fatigue in patients with plaque-type psoriasis: lack of an association with plasma cytokines

Background Fatigue is common in patients with psoriasis, and cytokines have been postulated to influence fatigue. Objective This case-control study explored the plasma levels of selected cytokines in patients with psoriasis and compared them with fatigue and other clinical factors. Materials and Methods Eighty-four patients with chronic plaque-type psoriasis and 84 age- and gender-matched healthy subjects were enrolled. Psoriasis severity was measured using the Psoriasis Area and Severity Index (PASI), and skin-related quality of life using the Dermatology Life Quality Index (DLQI). Fatigue was rated with the fatigue Visual Analogue Scale (fVAS). Plasma levels of interleukin (IL)-1 beta, IL-1R alpha, IL-1RII, IL-6, and IL-10 were measured by electrochemiluminescence sandwich immunoassay and ELISA. Results IL-1R alpha and IL-6 median concentrations were significantly higher in patients than healthy subjects: 203 pg/mL (interquartile range: 150-274) versus 166 pg/mL (128-212), p=0.008 for IL-R alpha, and 0.82 pg/mL (0.25-1.40) versus 0.50 pg/mL (0.25-0.91), p=0.009 for IL-6. IL-1 beta, IL-1RII, and IL-10 concentrations did not differ between patients and healthy subjects. Higher levels of IL-1R alpha and IL-6 were associated with increased body mass index (BMI), but not with disease activity. Cytokine concentrations were not associated with fatigue. Conclusion These findings do not support an association between fatigue and blood concentrations of selected pro- and anti-inflammatory cytokines. The increased IL-1R beta and IL-6 levels associated with increased BMI are probably caused by release of adipokines from adipose tissue; of these, leptin, in particular, is known to be a strong inflammatory stimulator.