A 55-year-old man with long-standing seropositive RA on methotrexate 25 mg/week presents with progressive dyspnea and dry cough over 2 months. HRCT shows bilateral ground-glass opacities with reticulation and traction bronchiectasis predominantly in the lower lobes. Pulmonary function tests show a restrictive pattern with reduced DLCO. What is the most likely diagnosis?
- A Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) ✓
- B Methotrexate-induced pneumonitis
- C Community-acquired pneumonia
- D Pulmonary tuberculosis
Correct answer: A. Rheumatoid arthritis-associated interstitial lung disease (RA-ILD)
Explanation
RA-ILD typically presents with a usual interstitial pneumonia (UIP) pattern: basal-predominant reticulation, traction bronchiectasis, and honeycombing on HRCT, with restrictive physiology and reduced DLCO. Methotrexate pneumonitis usually causes diffuse ground-glass opacities without basal predominance or honeycombing and often improves on drug withdrawal. The clinical picture of long-standing RA with progressive basal UIP is classic for RA-ILD.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.