Musculoskeletal manifestations in children with inflammatory bowel disease: a multicenter cohort study (GASTROREUM study)

Background: Musculoskeletal (MSK) symptoms are the most common extra-articular manifestations of pediatric-onset inflammatory bowel diseases (pIBD), and are associated with a more aggressive disease course. This study aims to characterize MSK manifestations in patients with pIBD, and to seek for predictors of persistently active arthritis one year after pIBD diagnosis. Methods: A multicenter, retrospective cohort study was conducted at 25 Italian pediatric rheumatology centers. Patients aged < 18 years with pIBD and MSK manifestations, followed for at least one year, were included. Data at onset of first MSK symptom, pIBD diagnosis, and one-year follow-up visit following pIBD diagnosis were collected. Results: A total of 180 patients were included, 111 (61.7%) with Crohn’s disease (CD), 55 (30.5%) with ulcerative colitis (UC), and 14 (7.8%) with unclassified IBD (IBDU). Arthralgia (72.8%) and arthritis (69.4%), were the most frequent MSK manifestations. Patients with CD had MSK symptoms prior to pIBD diagnosis more frequently than those with UC/IBDU (51.4% vs. 40.6%). Among the 125 patients with arthritis, 76.8% had peripheral arthritis, 14.4% had axial disease, and 8.8% had both peripheral and axial involvement. The most common articular pattern was oligoarthritis (52.0%), followed by monoarthritis (26.4%) and polyarthritis (21.6%). The most frequently affected joints were the knee, ankle, and hip. On multivariable analysis, antinuclear antibody (ANA) positivity (OR = 3.05, 95% CI: 1.05 – 8.89) and a polyarticular course of arthritis (OR = 3.42, 95% CI: 1.13–10.38) were independently associated with persistence of active arthritis at year 1 after pIBD diagnosis. Conclusions: Most patients with pIBD and arthritis presented with peripheral oligoarthritis affecting lower limb joints. A positive ANA status and development of polyarthritis predicted sustained arthritis activity.