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Rituximab-Induced ILD — SCE Rheumatology MCQ

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HardRheumatoid ArthritisRituximab-Induced ILDSCE Rheumatology

A 55-year-old woman with seropositive rheumatoid arthritis in sustained low disease activity receives rituximab because of persistent synovitis despite conventional synthetic DMARDs. She had no respiratory symptoms, and an HRCT performed four months before treatment was normal. Three weeks after her second 1-g rituximab infusion, she develops progressive exertional breathlessness, dry cough and hypoxaemia. HRCT now shows bilateral basal ground-glass opacities with an organising pneumonia pattern. Bronchoalveolar lavage cultures and PCR testing, including testing for Pneumocystis jirovecii, are negative. CT pulmonary angiography and echocardiography exclude pulmonary embolism and cardiac failure. What is the most likely diagnosis?

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Correct answer: D — Rituximab-induced interstitial lung disease

The most likely diagnosis is rituximab-induced interstitial lung disease. The decisive features are previously normal lung imaging, subacute symptoms shortly after rituximab exposure, bilateral ground-glass change with an organising pneumonia pattern, and exclusion of major infectious and cardiopulmonary alternatives. Rituximab-associated ILD is rare but recognised in autoimmune disease and may present with ground-glass opacities or organising pneumonia. Pneumocystis pneumonia remains an important initial differential in an immunosuppressed patient, but the negative BAL PCR and microbiology make it substantially less likely. Pulmonary embolism and cardiogenic oedema have been directly excluded. RA can itself cause organising pneumonia, but sustained low articular activity, normal recent HRCT and the close treatment–event relationship make a rituximab reaction more likely. Rituximab should be withheld while the diagnosis is assessed and glucocorticoid treatment considered with respiratory input.

Reference: Zamfir AS et al. Rituximab-Induced Interstitial Lung Disease: A Possible Underestimated Complication—A Systematic Review. Cancers. 2025;17:3786. https://pubmed.ncbi.nlm.nih.gov/41374988/