2695. Pneumocystis jirovecii Pneumonia in the Era of Effective Prophylaxis Following Hematopoietic Stem Cell Transplant

BACKGROUND: Pneumocystis jirovecii pneumonia is an uncommon and life-threatening disease that can occur following hematopoietic stem cell transplantation (HSCT). Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis greatly reduces the incidence of PJP. We aim to determine what factors contribute to the development of PJP following HSCT where TMP-SMX prophylaxis is widely used. METHODS: We performed a single-center, retrospective case series of HSCT recipients from January 1, 2012 to December 31, 2018. Subjects had clinical symptoms and radiographic evidence for PJP along with at least one positive Pneumocystis test obtained from bronchoalveolar lavage (BAL) including direct fluorescence antibody (DFA), quantitative polymerase chain reaction (qPCR), cytology, and pathology. RESULTS: 1111 subjects underwent HSCT; of whom, 25 (2.2%) met inclusion criteria and were treated for PJP. 6 were autologous and 19 were allogeneic HSCT recipients (1.23% and 3.05% of total autologous and allogeneic HSCT, respectively). All allogeneic HSCT recipients received in-vivo T-cell depletion. Median duration from autologous and allogeneic HSCT to PJP diagnosis were 138 days (range 20 to 348) and 346 days (range 41 to 771), respectively. PJP qPCR was positive in all samples tested (n = 20, range < 84 to 14900). DFA was positive in 6 (28%). Death from pneumonia occurred in 2 subjects; 11 (44%) required ICU stay, and 7 (27%) required intubation. At diagnosis, 3 subjects had relapse of underlying disease and 10 were on immunosuppression. 12 were on PJP prophylaxis (autologous HSCT n = 3), the most common of which was atovaquone (n = 5); only 2 subjects were on TMP-SMX. Cytomegalovirus (CMV) viremia was detected in 9 subjects (36%) prior to PJP diagnosis; 4 had pulmonary CMV coinfection. In total, 17 subjects (68%) had one of the above risk factors for PJP. Median total lymphocyte count and % lymphocytes were 5.1 × 10(3) cells/μL (range 1.4 to 38.5 × 10(3) cells/μL) and 9.6% (range 1.1 to 29.5%), respectively. CONCLUSION: PJP is an uncommon (2.2% of the study population) complication of HSCT while receiving PJP prophylaxis and in the absence of disease relapse, CMV reactivation, or ongoing immunosuppression. Presentation is often delayed in this population; a high degree of clinical suspicion should prompt diagnostic evaluation using a combination of laboratory tests on BAL fluid. [Image: see text] DISCLOSURES: All authors: No reported disclosures.