Abstract Introduction Pulmonary MALT lymphoma (mucosa-associated lymphoid tissue lymphoma) is a rare lung lymphoma that can present with pulmonary masses, pleural effusions, and lymphadenopathy. Its clinical and radiographic features overlap with other conditions like rheumatoid arthritis (RA)-related lung disease, which can also cause pleural effusions and pulmonary nodules. Differentiating these is crucial for appropriate treatment. Case Presentation A 46-year-old female, former smoker with a history of Wolff-Parkinson-White syndrome, patent foramen ovale, and prior pulmonary embolism, presented with persistent nonproductive cough and right-sided pleuritic chest pain. Chest radiography showed haziness in the right lung, suggesting a pleural effusion, confirmed by CT as a partially loculated effusion with pleural thickening. Thoracentesis revealed an exudative, sterile pleural effusion with elevated ADA and positive rheumatoid factor (RF), but no malignant cells. Her autoimmune work-up was positive only for RF. Rheumatology did not diagnose RA. A repeat CT scan showed resolution of the effusion but persistent pleural thickening, with new multifocal opacities and mild left hilar lymphadenopathy. Bronchoscopy was nondiagnostic. Robotic bronchoscopy with wedge resection and lymph node dissection revealed MALT lymphoma in the left lower lobe (LLL), but no immunoglobulin heavy chain (IgH) rearrangement. PET imaging showed FDG-avid lymphadenopathy consistent with Stage III pulmonary MALT lymphoma. A bone marrow biopsy was negative. Eight months later, the patient developed joint pain, and elevated RF titers suggested RA. She was started on methotrexate, and follow-up imaging showed improvement in pulmonary opacities. Given the resolution with methotrexate, the initial diagnosis of MALT lymphoma was reconsidered, with findings more consistent with RA-associated interstitial lung disease (ILD). Discussion Initially diagnosed with MALT lymphoma, the patient’s diagnosis evolved after rheumatology consultation for RA-related lung involvement. The radiographic progression and positive autoimmune markers suggested RA-induced lung disease rather than lymphoma. Methotrexate treatment improved both joint and pulmonary symptoms, pointing to RA-ILD. Methotrexate, a key therapy for RA, is effective in managing RA-ILD, which can mimic lymphoma. This case underscores the difficulty of diagnosing autoimmune lung diseases and the importance of considering RA-ILD in patients with persistent pleural effusions and autoimmune markers. This abstract is funded by: None
Tayyab et al. (Fri,) studied this question.