A69-01 Pneumocystis Jirovecii Pneumonia in a Patient One Year Post Axicabtagene Ciloleucel CAR-T Therapy for Follicular Lymphoma

Introduction CAR-T therapy induces profound and often prolonged immune dysfunction, including B-cell aplasia, hypogammaglobulinemia, and variable T-cell reconstitution, which together predispose patients to opportunistic infections. Pneumocystis jirovecii pneumonia (PJP) is classically associated with HIV/AIDS and other significant immunocompromised states. NCCN guidelines recommend PJP prophylaxis for at least 6 months post stem cell transplant or CAR-T therapy but there is limited data to guide optimal timing of discontinuation of PJP prophylaxis. Here we report a case of PJP occurring one year after axicabtagene ciloleucel (Yescarta) therapy. Case Presentation A 26-year-old female with a complex oncologic history, including DLBCL treated with R-CHOP and subsequent follicular lymphoma treated with RICE, autologous stem cell transplant, and axicabtagene ciloleucel CAR-T therapy 13 months prior, presented with acute hypoxic respiratory failure and intermittent fevers. Inflammatory markers were elevated (ESR and CRP) and respiratory viral panel was positive for rhino/enterovirus. CD4 count was 880 cells/μL and there was pan hypogammaglobulinemia. Chest CT revealed bilateral ground-glass opacities and bronchoscopy revealed Pneumocystis jirovecii by PCR. She had last received IVIG three months prior to admission and had discontinued prophylactic trimethoprim-sulfamethoxazole (TMP-SMX) one month prior to admission. She was treated with IV corticosteroids, IVIG, and a 21-day course of high-dose TMP-SMX. After clinical improvement, she completed an additional year of TMP-SMX therapy followed by continued PJP prophylaxis and ongoing IVIG. Discussion CAR-T therapy can induce depletion of normal B cells and dysregulation of immune function. Hypogammaglobulinemia is common post-CAR-T and may persist for over a year, placing patients at increased risk of bacterial and opportunistic infections. In CAR-T patients, CD4 may not reflect overall immune competence, Our patient had a normal CD4 count but developed PJP after stopping both IVIG and TMP-SMX, illustrating that some CAR-T recipients remain vulnerable to infection well beyond the typical post stem cell transplant timeframe. Retrospective studies and case series have documented delayed-onset opportunistic infections, including PJP, CMV, and fungal infections - beyond one year in CAR-T recipients, particularly those with delayed immune reconstitution or lapses in prophylaxis. Conclusion PJP can develop in CAR-T recipients well beyond the standard prophylaxis periods and CD4 counts alone may not reliably predict infection risk. This case suggests that individualized, risk-based strategies, including extended prophylaxis and immunoglobulin monitoring, should be considered to optimize post-CAR-T infection prevention. This abstract is funded by: None