Rituximab-Induced Lung Disease Presenting as Organizing Pneumonia in a Patient with Stable Rheumatoid Arthritis

Rituximab-induced lung disease (R-ILD) is a rare but potentially serious complication most commonly reported in patients receiving rituximab as part of combination chemotherapy for hematologic malignancies. Pulmonary toxicity associated with rituximab monotherapy in autoimmune disease remains underrecognized. We present a case of organizing pneumonia occurring in a patient with stable rheumatoid arthritis treated with rituximab monotherapy. Existing literature suggests that most reported cases occur in the setting of combination therapy, making this presentation uncommon. This case underscores the importance of maintaining a high index of suspicion for drug-induced lung disease in patients receiving rituximab who develop unexplained respiratory symptoms despite stable autoimmune disease. Early recognition and intervention may result in favorable clinical and radiographic outcomes.