Rituximab is now used to control antineutrophil cytoplasm antibody (ANCA)-associated vasculitides, eg, Wegener’s granulomatosis.1 2 In Churg–Strauss syndrome (CSS), a small-vessel systemic vasculitis with asthma and eosinophilia, 39% of patients have ANCA.3 4 Rituximab could be effective in ANCA-associated vasculitides, even if ANCA are not present at the time of prescription, because B lymphocytes also play a role as antigen-presenting cells and can modulate the immune response in another way than targeting antibody production. Therapy-refractory CSS5 was successfully treated with rituximab in three patients.6^–8 We would like to draw attention to the potential risk of rituximab-associated bronchospasm, by reporting …