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Methotrexate pneumonitis — SCE Rheumatology MCQ

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HardRheumatoid arthritisMethotrexate pneumonitisSCE Rheumatology

A 58-year-old man with rheumatoid arthritis has fever, pleuritic chest pain and dyspnoea three months after starting methotrexate. Oxygen saturations are 91% on air, chest CT shows diffuse bilateral ground-glass change, eosinophils are mildly raised and blood cultures are negative. CRP is 74 mg/L and pulmonary function tests had been normal before treatment. What is the most likely diagnosis?

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Correct answer: C — Methotrexate pneumonitis

Acute dyspnoea, fever and diffuse ground-glass change soon after methotrexate initiation are typical of methotrexate pneumonitis after infection has been considered. Rheumatoid ILD usually has a more chronic course, often with UIP or NSIP patterns. The teaching point is that methotrexate pneumonitis is uncommon but requires drug cessation and specialist respiratory assessment.

Reference: BNF; BSR csDMARD monitoring guideline 2025