Abstract / Summary
Abstract Severe drug-induced pneumonitis (DIP) during concurrent methotrexate and upadacitinib treatment is rarely reported and poses a considerable diagnostic and causality challenge. We report a white man in his late 50s with seropositive rheumatoid arthritis, treated with methotrexate and upadacitinib, who presented with progressive dyspnoea and hypoxaemia. He was initially treated for community-acquired pneumonia and subsequently developed severe ARDS despite maximal non-invasive respiratory support. Thoracic HRCT, together with expert opinion from the rheumatology and respiratory teams, indicated drug-induced pneumonitis as the most likely diagnosis, while an extensive infectious work-up, including testing for Pneumocystis jirovecii, was negative. He required invasive mechanical ventilation (IMV) and received intravenous methylprednisolone pulse-dose therapy (IVMP), 1 g once daily for three consecutive days, and five consecutive sessions of prone positioning, each for 18 hours, resulting in progressive, sustained improvement in oxygenation and respiratory mechanics, thereby averting the need for ECMO. He was successfully extubated after 8 days of IMV and subsequently discharged home 10 days post-extubation, without supplemental oxygen, on a tapering course of prednisolone. At the 3-month post-discharge follow-up, pulmonary function testing revealed resolution of the baseline obstructive pattern and a decline in gas transfer while on prednisolone as the sole DMARD. This case highlights the importance of promptly withdrawing suspected causative agents, rigorously excluding infection and other alternative diagnoses, and escalating respiratory support to IMV and corticosteroid therapy to IVMP when severe DIP continues to progress despite initial treatment.