Fig. 17

Differential diagnosis of RB-ILD. a Axial CT image depicts subacute hypersensitivity pneumonitis (HP) in a 71-year-old woman with a long history of exposition to moldy hay (farmer’s lung). Imaging findings of HP are similar to RB-ILD, which also appears as centrilobular nodules predominantly in the upper lobes (arrow) and patchy areas of ground-glass attenuation. A clinical history is crucial to make the differential diagnosis. b Sarcoidosis in a 37-year-old man. Axial CT image shows diffuse areas of nodularity with peribronchial distribution and also in relation to the subpleural region (arrow). There are also some surrounding ground-glass opacities