Interleukin-33 as a marker of disease activity in rheumatoid factor positive polyarticular juvenile idiopathic arthritis.

Objective: To investigate clinical usefulness of serum interleukin (IL)-33 levels as an indicator of disease activity in juvenile idiopathic arthritis (JIA).

Methods: We measured serum levels of IL-33 in 39 patients with JIA, including 7 patients with rheumatoid factor positive poly-JIA (RF + poly-JIA), 8 patients with RF negative poly-JIA (RF-poly-JIA), 20 patients with oligoarticular JIA (Oligo-JIA), 4 patients with enthesitis-related arthritis (ERA) and 30 age-matched healthy controls. Furthermore, we determined their correlation with measures of disease activity.

Results: Serum IL-33 levels in patients with RF + poly-JIA were significantly elevated compared to those in patients with RF-poly-JIA, oligo-JIA and HC. Serum IL-33 levels in patients with RF-poly-JIA, oligo-JIA and ERA were not elevated compared to those in HC. Serum IL-33 levels in RF + poly-JIA patients normalized in remission phase. Serum IL-33 levels correlated positively with RF in patients with RF + poly-JIA.

Conclusions: These results indicate that serum IL-33 levels in RF + poly-JIA patients correlated with disease activity, suggesting a potential role of IL-33 as a promising indicator of disease activity.