Abstract Introduction Pulmonary complications are frequent in patients with Human Immunodeficiency Virus (HIV) infection, most often due to opportunistic infections such as Pneumocystis jirovecii pneumonia (PJP) or tuberculosis. However, malignant etiologies, including Plasmablastic Lymphoma (PBL) - a rare, aggressive variant of diffuse large B-cell lymphoma - can mimic infection both clinically and radiographically. Early recognition is critical given its poor prognosis and distinct therapeutic approach. Case Report A 40-year-old male with no prior medical history presented with three weeks of cough, intermittent hemoptysis, pleuritic chest pain, fever, night sweats, and weight loss. Physical examination revealed bilateral cervical and axillary lymphadenopathy and diffuse rhonchi. Initial chest radiograph demonstrated multifocal patchy consolidative opacities concerning for multifocal pneumonia (Figure 1). Computed tomography (CT) of the chest showed extensive peribronchovascular flame-shaped consolidations, perilymphatic nodularity, and diffuse mediastinal and axillary lymphadenopathy, suggestive of an atypical infection or lymphoproliferative process.HIV-1 testing was positive with a CD4 count of 149 cells/µL. Noninvasive workup, including Pneumocystis jirovecii, fungal, and Mycobacterium tuberculosis testing, was negative. The patient was initiated on antiretroviral therapy (bictegravir/emtricitabine/tenofovir alafenamide). Given persistent abnormalities, bronchoscopy with bronchoalveolar lavage, brushings, and endobronchial ultrasound-guided (EBUS) transbronchial biopsies was performed. The airways were noted to be irregular and narrowed in the left upper and lower lobes, with bulky subcarinal lymphadenopathy. Pathology revealed sheets of plasmablast-like cells positive for CD138, MUM1, CD38, and Epstein-Barr virus-encoded RNA (EBER), but negative for CD20 and PAX5, consistent with Plasmablastic Lymphoma. Following the procedure, the patient developed a small left apical pneumothorax, managed conservatively with supplemental oxygen. He subsequently initiated dose-adjusted EPOCH chemotherapy alongside antiretroviral therapy. Discussion This case highlights pulmonary PBL as a rare but important cause of diffuse pulmonary infiltrates in HIV-positive patients. Its radiographic presentation can closely resemble opportunistic infection or Kaposi sarcoma, delaying diagnosis. A high index of suspicion and early tissue sampling via bronchoscopy are essential for accurate diagnosis. Prompt recognition and initiation of combined chemotherapy and antiretroviral therapy are crucial for improved outcomes in this highly aggressive lymphoma. Figure 1: Chest CT showing multifocal patchy airspace opacities predominantly in the perihilar and lower lung zones. References: 1. Castillo JJ et al. Plasmablastic lymphoma: a systematic review. Lancet Oncol. 2008;9(6):559-567. 2. Loghavi S et al. Pulmonary plasmablastic lymphoma: a diagnostic pitfall in HIV-positive patients. Am J Surg Pathol. 2015;39(4):543-551. 3. Morscio J et al. Clinicopathologic comparison of plasmablastic lymphoma in HIV-positive and HIV-negative patients. Histopathology. 2014;65(2):230-242. This abstract is funded by: none
B George (Fri,) studied this question.