A 62-year-old man with long-standing RA on methotrexate and leflunomide presents with subacute onset of bilateral lower lobe crackles, reduced exercise tolerance, and high-resolution CT showing ground-glass opacities with honeycombing in basal segments. Pulmonary function tests show FVC 65% predicted, DLCO 55%. The MOST likely diagnosis and the AAC-based pattern is:
- A Methotrexate pneumonitis — organizing pneumonia (OP) pattern on HRCT
- B RA-associated ILD — nonspecific interstitial pneumonia (NSIP) pattern
- C RA-associated ILD — usual interstitial pneumonia (UIP) pattern ✓
- D Rheumatoid lung nodules with secondary bronchopleural fistula
Explanation
RA-ILD is the most serious pulmonary complication of rheumatoid arthritis. The UIP pattern (honeycombing with basal reticulation, traction bronchiectasis, subpleural distribution) on HRCT portends the worst prognosis, similar to idiopathic pulmonary fibrosis. UIP is the predominant pattern in RA-ILD (~60%), while NSIP (ground-glass without honeycombing, bilateral basal) is second most common. Methotrexate pneumonitis typically shows bilateral ground-glass opacities (hypersensitivity pneumonitis pattern, eosinophilia) without honeycombing, and usually reverses with drug withdrawal. The honeycombing pattern here strongly favors RA-UIP over MTX pneumonitis.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.