Rituximab-induced interstitial lung disease presenting as acute respiratory distress syndrome: a case report

Abstract Background Rituximab-induced interstitial lung disease (RTX-ILD) is an uncommon but potentially fatal adverse event that may closely resemble infectious pneumonia, leading to delayed diagnosis and treatment. Case presentation A 59-year-old woman with neuromyelitis optica spectrum disorder developed fever, cough, and rapidly progressive dyspnoea six weeks after a single 500 mg intravenous rituximab infusion. High-resolution computed tomography demonstrated bilateral air-space opacities with a crazy-paving pattern. Comprehensive microbiological evaluation, including bronchoalveolar lavage for bacterial, mycobacterial, fungal, Pneumocystis jirovecii, and viral pathogens, was negative. Despite empirical antibiotics, she progressed to acute respiratory distress syndrome requiring invasive mechanical ventilation. Rituximab-induced ILD was diagnosed based on the temporal association, exclusion of alternative causes, and a Naranjo score of 7. High-dose corticosteroid therapy resulted in marked clinical and radiological improvement. Conclusion RTX-ILD should be suspected in patients presenting with respiratory deterioration within weeks of rituximab exposure. Prompt exclusion of infection, early recognition, withholding of further rituximab therapy, and timely corticosteroid therapy are essential to improve outcomes in this potentially life-threatening condition.