A 55-year-old woman with longstanding seropositive RA on methotrexate 20 mg weekly is started on a biologic. Three months later she develops sudden onset fever, dry cough, progressive dyspnoea, and hypoxia. High-resolution CT shows bilateral ground-glass opacities. Bronchoscopy lavage shows lymphocytosis. What is the MOST likely cause?
- A RA-associated interstitial lung disease progression
- B Pneumocystis jirovecii pneumonia
- C Methotrexate-induced pneumonitis ✓
- D TNF-inhibitor reactivation of latent TB
Correct answer: C. Methotrexate-induced pneumonitis
Explanation
Methotrexate pneumonitis is a dose-independent hypersensitivity reaction that can occur at any time during therapy, presenting with subacute dyspnoea, dry cough, fever, and bilateral ground-glass opacities on HRCT. BAL lymphocytosis is characteristic. It can mimic infection or ILD progression. Management requires immediate methotrexate withdrawal and corticosteroids. PJP is possible with immunosuppression but BAL would show cysts/trophozoites, not lymphocytosis.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.