We aimed to assess risk factors for the development of severe infection in patients with antineutrophil cytoplasm antibody-associated vasculitis (AAV) receiving rituximab.

192 patients with AAV were identified. Univariate and multivariate analyses were performed to identify risk factors for severe infection following rituximab. Severe infections were classified as grade ≥3 as proposed by the Common Terminology Criteria for Adverse Events V.4.0.

95 severe infections were recorded in 49 (25.52%) patients, corresponding to an event rate of 26.06 per 100 person-years. The prophylactic use of trimethoprim-sulfamethoxazole was associated with a lower frequency of severe infections (HR 0.30, 95% CI 0.13 to 0.69), while older age (HR 1.03, 95% CI 1.01 to 1.05), endobronchial involvement (HR 2.21, 95% CI 1.14 to 4.26), presence of chronic obstructive pulmonary disease (HR 6.30, 95% CI 1.08 to 36.75) and previous alemtuzumab use (HR 3.97, 95% CI 1.50 to 10.54) increased the risk. When analysis was restricted to respiratory tract infections (66.3% of all infections), endobronchial involvement (HR 4.27, 95% CI 1.81 to 10.06), severe bronchiectasis (HR 6.14, 95% CI 1.18 to 31.91), higher neutrophil count (HR 1.19, 95% CI 1.06 to 1.33) and major relapse (HR 3.07, 95% CI 1.30 to 7.23) as indication for rituximab use conferred a higher risk, while refractory disease (HR 0.25, 95% CI 0.07 to 0.90) as indication had a lower frequency of severe infections.

We found severe infections in one quarter of patients with AAV receiving rituximab. Trimethoprim-sulfamethoxazole prophylaxis reduced the risk, while especially bronchiectasis and endobronchial involvement are risk factors for severe respiratory infections.