A69-08 An Opportunistic Clue to a Hidden Malignancy: Pneumocystis Jirovecii Pneumonia Revealing Adult T-Cell Leukemia

Introduction Adult T Cell Leukemia/-Lymphoma (ATL) is a rare malignancy caused by chronic infection with human T-cell lymphotropic virus type 1 (HTLV-1), affecting approximately 0.6/100,000 individuals in the United States. The viral strain is highly prevalent in the Caribbean islands, and common forms of transmission include vertical transmission and sexual contact; chronic viral carriers can go on to develop ATL or a degenerative myelopathy. The virus commonly infects T-lymphocytes and due to impaired CD4+ function, patients are at increased risk for opportunistic infections. Pneumocystis jirovecii pneumonia (PJP), while classically associated with HIV infection, is rarely reported in patients with ATL. Case Presentation A 35-year-old female, recently emigrated from Jamaica, presented with a one-month history of nonproductive cough and dyspnea. Laboratory evaluation revealed leukocytosis, and chest CT demonstrated diffuse, upper-lobe predominant interstitial infiltrates with a left anterior mediastinal soft-tissue mass. She was empirically treated for community-acquired pneumonia while fungal and mycobacterial studies were obtained. A bronchoscopy with bronchoalveolar lavage identified PJP. She was initiated on trimethoprim-sulfamethoxazole and later transitioned to atovaquone due to gastrointestinal intolerance. Workup for immunodeficiency revealed negative HIV testing and low IgM levels. A biopsy of the pleural based mass performed via video assisted thoracoscopy which revealed benign cystic pathology. However, a repeat outpatient chest CT demonstrated interval development of a large left hilar mass, prompting readmission. Repeat labs revealed lymphocyte-predominant leukocytosis, and flow cytometry identified an atypical CD4+/CD30+ T-cell population and clonal T-cell receptor gene rearrangement. HTLV serologies returned positive for HTLV-1. Repeat bronchoscopy identified extrinsic compression of LUL and LLL, and biopsy of the hilar mass was consistent with CD4+/CD30+ T-cell lymphoproliferative disorder; retrospective analysis of the mediastinal mass also confirmed the same pathology. Hematology formally diagnosed her with chronic ATL with unfavorable prognostic factors and she is currently exploring treatment options. Discussion PJP should always prompt evaluation for underlying immunodeficiency, particularly when identified in patients without HIV infection or immunosuppressive therapy. Trimethoprim-sulfamethoxazole remains the first-line treatment, with atovaquone serving as an effective alternative. Adjunctive corticosteroids, while well-established in HIV-associated PJP, may also provide benefits in other immunocompromised hosts. This case underscores the diagnostic challenge of PJP as a sentinel event revealing an occult hematologic malignancy. Conclusion Pneumocystis jirovecii pneumonia can be an initial manifestation of HTLV-1-associated ATL, a rare but important cause of immunodeficiency. Recognition of this association is critical to ensure timely diagnosis and management of both the infectious and malignant processes.