Mild Restrictive Lung Disease Pattern

A 62-year-old woman with rheumatoid arthritis presents with progressive exertional dyspnea and dry cough over 14 months. Examination reveals fine end-inspiratory crackles at lung bases, SpO2 91% at rest, and desaturation to 85% on 6-minute walk. HRCT shows UIP pattern with basal honeycombing. Spirometry shows FEV1 1.65 L (72% predicted), FVC 2.10 L (68% predicted), and FEV1/FVC 0.79. The flow-volume loop demonstrates a narrow, tall morphology with reduced volume and preserved peak expiratory flow. Body plethysmography shows TLC 3.85 L (65% predicted). The pattern marked **A** in the diagram — normal FEV1/FVC >0.70 with proportional reduction in both FEV1 and FVC, and reduced TLC <80% — confirms which diagnosis?