A 32-year-old woman with a history of rheumatoid arthritis presents with progressive dyspnea and a dry cough over 6 months. High-resolution CT chest shows bilateral interstitial infiltrates. Spirometry reveals: FEV₁ = 68% predicted, FVC = 62% predicted, FEV₁/FVC ratio = 1.10. What is the spirometric pattern, and what is the most likely pulmonary complication?

Explanation

## Spirometric Pattern Identification **Key Point:** In this case, FEV₁/FVC = 1.10 (> 0.70), which rules out obstruction. Both FEV₁ and FVC are reduced proportionally (68% and 62%, respectively), which is the hallmark of a **restrictive pattern**. **High-Yield:** Restrictive pattern criteria: - FEV₁/FVC ≥ 0.70 (normal or elevated ratio) - Reduced FVC (typically < 80% predicted) - Reduced FEV₁ (proportional to FVC reduction) ## Rheumatoid Arthritis and Pulmonary Involvement | Pulmonary Complication | Frequency | Spirometric Pattern | HRCT Finding | |---|---|---|---| | Rheumatoid pulmonary fibrosis (RPF) | 20–30% | Restrictive | Bilateral interstitial infiltrates, UIP pattern | | Pleural effusion | 5–10% | Restrictive (if large) | Pleural fluid | | Bronchiectasis | 5–10% | Mixed or obstructive | Bronchial wall thickening | | Rheumatoid nodules | Rare | Normal or restrictive | Nodules ± cavitation | **Clinical Pearl:** Rheumatoid pulmonary fibrosis (RPF) is the most common serious pulmonary manifestation of RA. It typically presents with insidious dyspnea, dry cough, and restrictive spirometry. HRCT showing bilateral interstitial infiltrates is classic. **Mnemonic: Restrictive = Reduced FVC with preserved FEV₁/FVC ratio** — the lungs are "stiff," so both volumes drop together, but the ratio stays normal or high.