Pneumocystis jirovecii Pneumonia in an Adolescent With Acute Lymphoblastic Leukemia Due to Non-adherence to Prophylaxis: A Case Report

Pneumocystis jirovecii pneumonia (PJP) is a severe and potentially life-threatening opportunistic infection in immunocompromised patients, especially those with hematologic malignancies.Although routine prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) has significantly reduced its incidence, breakthrough infections still occur, most commonly due to poor adherence to prophylactic therapy.This case report highlights the risks of non-adherence to PJP prophylaxis in adolescents and underscores the importance of early diagnostic suspicion and multidisciplinary management.A 15-year-old female patient with acute lymphoblastic leukemia presented during her seventh month of maintenance therapy (methotrexate and 6-mercaptopurine) in a compromised general condition with tachycardia, tachypnea, and hypoxemia, following a 24-hour history of fever and dry cough.Heteroanamnestic data revealed prolonged non-adherence to TMP-SMX prophylaxis.Imaging showed diffuse bilateral interstitial infiltrates on chest radiography and ground-glass opacities on high-resolution computed tomography (HRCT).PJP was confirmed via polymerase chain reaction (PCR) from bronchoalveolar lavage and a positive serum 1,3-β-Dglucan test.Treatment included intravenous TMP-SMX, corticosteroids, and high-flow nasal cannula oxygen therapy.The course was complicated by pancytopenia, likely secondary to TMP-SMX, and febrile neutropenia.A multidisciplinary approach, including social and psychiatric support, addressed nonadherence.The patient was discharged in good condition; maintenance therapy was continued, and prophylaxis was switched to monthly aerosolized pentamidine administered in the hospital setting.PJP prevention in pediatric oncology remains a significant challenge, as inconsistent adherence can rapidly lead to severe clinical deterioration.Our experience suggests that successful outcomes depend on addressing psychosocial barriers early.Transitioning to supervised, hospital-administered alternatives, such as aerosolized pentamidine, alongside multidisciplinary support, may help ensure adherence to prophylaxis in vulnerable oncology patients.