New-onset Hypogammaglobulinemia and Infectious Complications Associated with Rituximab Use in Childhood-onset Rheumatic Diseases.

Objective To investigate the incidence and risk factors for hypogammaglobulinemia and infectious complications associated with rituximab treatment in childhood-onset rheumatic diseases. Methods We performed a single-center retrospective study of patients (n = 85) treated at Boston Children's Hospital (BCH) from 2009 to 2019. Study subjects included patients (ages 6 to 24) who received rituximab for the treatment of a childhood-onset rheumatic disease. Results New-onset hypogammaglobulinemia developed in 23 (27.1%) patients within 18 months of rituximab induction treatment. 22 patients (25.9%) developed at least one infectious complication in the 18 months following the first rituximab infusion; of these, 11 (50%) had serious infections requiring inpatient treatment. After adjusting for potential confounders, exposure to pulse corticosteroid therapy in the month prior to rituximab use was a significant predictor of both new-onset hypogammaglobulinemia (OR 3.94; 95% CI 1.07-16.0; p = 0.044) and infectious complications (OR 15.3; 95% CI 3.04-126.8; p = 0.003). Post-rituximab hypogammaglobulinemia was the strongest predictor of serious infectious complications (OR 7.89; 95% CI 1.41-65.6; p = 0.028). Younger age at rituximab use was also a significant predictor of new-onset hypogammaglobulinemia (OR 0.83; 95% CI 0.70-0.97; p = 0.021). Compared with other rheumatic diseases, patients with vasculitis had a higher likelihood of developing infectious complications, including serious infections. Conclusion Although rituximab was well tolerated in terms of infectious complications in the majority of patients with childhood-onset rheumatic diseases, a substantial proportion developed new-onset hypogammaglobulinemia and infectious complications following treatment. Our study highlights a role for heightened vigilance of rituximab-associated hypogammaglobulinemia and infections in pediatric patients with rheumatic conditions.