The effectiveness and safety of rituximab in juvenile idiopathic arthritis: Hints from the ITHACA monocentric registry

B cells contribute to the pathogenesis of juvenile idiopathic arthritis (JIA), suggesting a therapeutic potential for B cell depleting agent rituximab (RTX). This retrospective study describes the effectiveness and safety of RTX in a monocentric cohort of JIA patients. Disease activity was assessed using DAS28-CRP at baseline and at each RTX infusion. Thirty-seven JIA patients (56.8 % with polyarticular JIA) received RTX between 2008 and 2023, at a median age of 23.5 years. Most patients had a refractory disease: 45.9 % of the cohort received >2 prior biologics. The median exposure time to RTX was 2.5 years, with a median number of 5 cycles per patient and a median follow-up from first infusion of 7.44 years. At 6 months, 73 % of patients responded to RTX, and 48.6 % achieved remission. At 12 months, the trend in reducing DAS28-CRP levels persisted. ACPA positivity improved remission rates although not significantly; in most cases, uveitis did not respond to RTX. Six patients (16.2 %) discontinued RTX thanks to a prolonged remission, none requiring further biologics at a follow-up of 1.4 years. Both hypogammaglobulinemia and clinically relevant infections occurred in 27 % of the cohort. Receiving >4 RTX cycles predicted the development of hypogammaglobulinemia and/or infections (sensitivity 71.9 %, specificity 60.0 %). Although the optimal patient selection strategy remains unclear, RTX might be regarded as an effective treatment for refractory cases, particularly in oligo/polyarticular JIA, with a manageable safety profile when exposure is limited to 4 cycles.