Infectious risk when prescribing rituximab in patients with hypogammaglobulinemia acquired in the setting of autoimmune diseases

•Rituximab has been used in autoimmune diseases other than rheumatoid arthritis.•Hypogammaglobulinemia is a well-known side effect of rituximab treatment.•Hypogammaglobulinemia has been associated with an increased risk of infection.•Prescriber may decide to initiate or continue rituximab despite hypogammaglobulinemia.•There are few data depicting infectious risk after acquired hypogammaglobulinemia. We conducted a single-centre retrospective cohort study in a French University Hospital between 2010 and 2018 to describe the risk of severe infectious event (SIE) within 2 years after the date of first rituximab infusion (T0) prescribed after the evidence of acquired hypogammaglobulinemia (gamma globulins [GG] ≤ 6 g/L) in the setting of autoimmune diseases (AID) other than rheumatoid arthritis. SIE occurred in 26 out of 121 included patients. Two years cumulative incidence rates were 12.7 % (95 % CI 5.1–23.9) in the multiple sclerosis/neuromyelitis optica spectrum disorder group (n = 48), 27.6 % (95 % CI 15.7–40.9) in the ANCA-associated vasculitis group (n = 48) and 30.6 % (95 % CI 13.1–50.3) in the ‘other AID’ group (n = 25). Median GG level at T0 was 5.3 g/l (IQR 4.1–5.6) in the 'SIE' group and 5.6 g/l (IQR 4.7–5.8) in the 'no SIE' group (p = 0.04). In regression analysis, risk of SIE increased with Charlson comorbidity index ≥ 3 (OR 2.77; 95 % CI 1.01–7.57), lung disease (OR 3.20; 95 % CI 1.27–7.99), GG