Epstein-Barr Virus (EBV)-Positive Diffuse Large B-cell Lymphoma Masquerading As Lupus Pneumonitis in a Young Woman With Systemic Lupus Erythematosus: A Diagnostic Odyssey.

Patients with systemic lupus erythematosus (SLE) are at increased risk for lymphoma compared to the general population. While pulmonary manifestations are common in SLE, diffuse micronodular patterns can resemble infection, granulomatous disease, or malignancy, making diagnosis challenging. A 21-year-old woman with childhood-onset SLE (class IV lupus nephritis) on mycophenolate mofetil and hydroxychloroquine presented with progressive dyspnea and diffuse bilateral pulmonary micronodularity. Initial bronchoscopy and biopsy showed non-specific perivascular inflammation, negative for malignancy or infection. She initially responded to steroids with near-complete radiographic resolution. Over the next nine months, however, she developed recurrent pulmonary nodules unresponsive to increased immunosuppression. Repeat bronchoscopy revealed necrotizing granulomatous inflammation without identifiable organisms. Her condition progressed to respiratory failure, necessitating a surgical lung biopsy. Video-assisted thoracoscopic surgery (VATS) wedge resection identified Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma arising in immune deficiency/dysregulation, with an EBV PCR of 25,500 IU/mL. Postoperatively, she developed acute respiratory failure requiring extracorporeal membrane oxygenation (ECMO) and hemophagocytic lymphohistiocytosis (HLH). She completed six cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) chemotherapy. End-of-treatment PET/CT showed persistent hypermetabolic pulmonary nodules (Deauville score 5), and she is now being evaluated for chimeric antigen receptor (CAR) T-cell therapy. This case highlights the challenge of distinguishing lymphoproliferative disorders from autoimmune lung disease in immunosuppressed SLE patients. Initial steroid responsiveness does not rule out malignancy. Clinicians should maintain a high suspicion for lymphoma in SLE patients with atypical or refractory pulmonary symptoms, especially those on chronic immunosuppression.