Similar to Image 5, this is an HRCT in a patient with biopsy-proven RB-ILD. HRCT shows scattered ill-defined centrilobular nodules of ground-glass opacity (red arrows) involving all lung regions. These nodules correspond to the peribronchiolar macrophage infiltrates, inflammation, and fibrosis seen on histologic sections in these patients. No other abnormalities are visible. The differential diagnosis of a patient with this HRCT appearance would include other causes of cellular bronchiolitis, such as hypersensitivity pneumonitis, atypical infections (particularly pneumocystis and viral infections), and follicular bronchiolitis.