Reports in haematology, transplantation medicine and rheumatology indicate that Rituximab, a B cell depleting therapy, increases the risk for Pneumocystis jiroveci pneumopathy. Patients with antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis have an increased incidence of P. jiroveci pneumopathy compared to other autoimmune diseases and Rituximab is often used to induce and maintain remission. Herein, we present a case of a patient with granulomatosis with polyangiitis treated with Rituximab for relapse that developed P. jiroveci pneumopathy 3 months after and we review the relevant literature to assess P. jiroveci pneumopathy incidence and risks factors under Rituximab. We also discuss whether P. jiroveci screening before Rituximab and P. jiroveci pneumopathy prophylaxis under Rituximab are indicated. P. jiroveci colonisation is found in 25 % of patients with autoimmune diseases. However, the association between colonisation and P. jiroveci pneumopathy development is not very strong. P. jiroveci pneumopathy incidence in ANCA-associated vasculitis patients treated with Rituximab is found to be 1.2 %. Therefore, evidence and practice do not support the use of P. jiroveci pneumopathy chemoprophylaxis in all ANCA-associated vasculitis patients receiving Rituximab. CD4 cell count cut-off does not work well in patients treated with Rituximab as it does not reflect T cell impairment following B cell depletion. To help stratify the risk of both colonisation and P. jiroveci pneumopathy development, assessment of the patient's net state of immunodeficiency before administering Rituximab-including age, renal or lung involvement, previous infections due to T cell dysfunction, blood tests (lymphocytopenia, low CD4 cell count) and concomitant therapy-is warranted.