Patterns of clinical joint inflammation in juvenile idiopathic arthritis

Abstract

Objectives: We studied patterns of joint inflammation in juvenile idiopathic arthritis (JIA) to assess whether joint activity recurs locally in the same joints.

Methods: Joints of 91 patients of the BeSt for Kids study, a treat-to-target trial for children with recent-onset oligoarticular, rheumatoid factor-negative polyarticular and psoriatic JIA, were clinically assessed during 2 years (10 study visits). The association between joint inflammation at baseline and later inflammation in the same joint was assessed using a multilevel mixed-effects logistic regression model at joint level. With a Poisson model, the association between baseline joint inflammation and the number of study visits at which the same joint was recurrently inflamed was tested.

Results: Of the 6097 joints studied, 15% (897) was clinically inflamed at baseline. In 42% (377/897) of those joints, inflammation recurred during follow-up. Joint inflammation at baseline was statistically significantly associated with joint inflammation during follow-up in the same joint (OR 3.9, 95% CI 3.5 to 4.4) and specifically with the number of episodes of recurrent joint inflammation (IRR 1.6, 95% CI 1.2 to 2.1).

Conclusion: In JIA, joint inflammation has the tendency to recur multiple times in joints that are clinically inflamed at disease onset. This indicates that local factors might play a role in the processes contributing to the occurrence of JIA flares.

Keywords: Inflammation; Juvenile Idiopathic Arthritis; Synovitis.

Figure 1

Joint inflammation patterns in the three JIA types (oligoarticular, n=11; RF-negative polyarticular, n=72, psoriatic, n=8) included in the BeSt for Kids study. MCP, metacarpophalangeal; PIP, proximal interphalangeal; DIP, distal interphalangeal; MTP, metatarsophalangeal