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Objectives Rituximab has become the cornerstone of induction treatment in ANCA-associated vasculitis (AAV). B-cell depletion may increase the risk of hypogammaglobulinemia, potentially leading to severe infections. This study aims to assess factors associated with hypogammaglobulinemia in AAV patients treated with rituximab. Methods This retrospective cohort study included AAV patients treated with rituximab induction in 14 European centres. Severe adverse events (SAEs) were defined as episodes requiring hospitalization or intravenous antibiotics, malignancies, or death. Linear and logistic regression were used to identify predictors of IgG levels and of the risk of hypogammaglobulinemia, defined as IgG ≤7 g/l at 6 months. Results The study included 227 patients. IgG levels at 6 months were lower than baseline (P  < 0.001). Patients requiring intravenous antibiotics during the first 6 months had lower IgG levels at 6 months (P  = 0.004). Age [β (95% CI): −0.23 (−0.38, −0.08) per 10 years, P  = 0.003], oral glucocorticoid dose at induction [β (95% CI): −0.37 (−0.51, −0.24) per sqrt-transformed mg prednisone, P  < 0.001] and concomitant use of intravenous glucocorticoid pulses [β (95% CI): −0.88 (−1.73, −0.02), P  = 0.044] were associated with IgG levels at 6 months. Hypogammaglobulinemia was identified in 97 (42.7%) patients. In multivariable logistic regression, factors associated with the risk of hypogammaglobulinemia were age [OR (95% CI): 1.46 (1.15, 1.86) per 10 years, P  = 0.002] and oral glucocorticoid dose at induction [OR (95% CI): 1.52 (1.23, 1.89) per 10 mg prednisone, P  < 0.001]. Conclusions In AAV patients treated with rituximab, hypogammaglobulinemia at 6 months after induction is common, and lower IgG levels are associated with serious infections. The risk of hypogammaglobulinemia in these patients increases with age and higher glucocorticoid doses. [ABSTRACT FROM AUTHOR]

Objective To identify and characterize genetic loci associated with the risk of developing ANCA-associated vasculitides (AAV). Methods Genetic association analyses were performed after Illumina sequencing of 1853 genes and subsequent replication with genotyping of selected single nucleotide polymorphisms in a total cohort of 1110 Scandinavian cases with granulomatosis with polyangiitis or microscopic polyangiitis, and 1589 controls. A novel AAV-associated single nucleotide polymorphism was analysed for allele-specific effects on gene expression using luciferase reporter assay. Results PR3-ANCA+ AAV was significantly associated with two independent loci in the HLA-DPB1/HLA-DPA1 region [rs1042335, P  = 6.3 × 10−61, odds ratio (OR) 0.10; rs9277341, P  = 1.5 × 10−44, OR 0.22] and with rs28929474 in the SERPINA1 gene (P  = 2.7 × 10−10, OR 2.9). MPO-ANCA+ AAV was significantly associated with the HLA-DQB1/HLA-DQA2 locus (rs9274619, P  = 5.4 × 10−25, OR 3.7) and with a rare variant in the BACH2 gene (rs78275221, P  = 7.9 × 10−7, OR 3.0), the latter a novel susceptibility locus for MPO-ANCA+ granulomatosis with polyangiitis/microscopic polyangiitis. The rs78275221-A risk allele reduced luciferase gene expression in endothelial cells, specifically, as compared with the non-risk allele. Conclusion We identified a novel susceptibility locus for MPO-ANCA+ AAV and propose that the associated variant is of mechanistic importance, exerting a regulatory function on gene expression in specific cell types. [ABSTRACT FROM AUTHOR]