AbstractIntroductionPneumocystis jirovecii pneumonia (PJP) is a rare complication of hematopoietic stem cell transplantation (HSCT). Primary prophylaxis for 6–12 months post‐HSCT is the standard approach. However, there is no consensus regarding the optimal duration of prophylaxis.MethodsWe identified patients who developed PJP more than 1‐year post‐HSCT. All patients had previously received 12 months of PJP prophylaxis. PJP was diagnosed based on clinical findings and the detection of P. jirovecii in bronchoalveolar lavage (BAL) using polymerase chain reaction (PCR). The CD4⁺ T‐cell percentage was determined using flow cytometry. Data expressed as median (interquartile range).ResultsTen patients developed PJP at 17.5 months (16–24 months) post‐HSCT. PJP diagnosis occurred 5.5 months (3–15 months) after discontinuing prophylaxis. Eight patients received anti‐thymocyte globulin (ATG) as graft versus host disease (GVHD) prophylaxis. At diagnosis, only one patient had lymphopenia; all patients had CD4⁺ T‐lymphocyte counts ≥0.2 × 10⁹/L (median 0.337 × 10⁹/L). Three patients had concomitant bacterial infections. The clinical presentation was mild; only three required hospitalization, none of them required intensive care and there were no deaths.ConclusionThere is a need to develop risk‐adapted prophylactic strategies in the contemporary era using ATG‐based GVHD prophylaxis.