Dry cough and breathlessness in a woman on methotrexate

A 55-year-old woman presented to the respiratory clinic with a two-week history of dry cough and progressive breathlessness. She had been diagnosed with rheumatoid arthritis six months earlier. Four months ago, she was started on methotrexate 15 mg once weekly and folic acid 5 mg daily. Three months ago, hydroxychloroquine 200 mg daily was added. Two weeks ago, she developed a dry cough and noticed that she became short of breath after walking up one flight of stairs. Over the last few days, her breathlessness has worsened, and she is now breathless on minimal exertion. On examination, she was tachypnoeic with a respiratory rate of 28 breaths per minute, and she had fine crepitations bilaterally in the lung bases. Her oxygen saturation was 91% on room air. She had small joint swan neck deformities consistent with long-standing rheumatoid arthritis. Chest radiograph showed bilateral interstitial infiltrates, and high-resolution CT confirmed bilateral ground-glass opacities with a predominantly basal distribution. Blood tests showed a slightly raised white cell count with no eosinophilia, an elevated CRP of 45 mg/L, and normal renal and liver function. Sputum microscopy and culture were negative, and viral PCR for common respiratory viruses was negative. She was admitted for supplemental oxygen and supportive care. Her regular medications were continued, but the methotrexate was withheld. Within 72 hours, her respiratory symptoms began to improve, and by day seven, her oxygen saturation was 96% on room air. Repeat chest imaging at day seven showed partial resolution of the infiltrates. No rechallenge was undertaken.