Air Trapping – Hypersensitivity Pneumonitis Bird Fancier’s Disease

55-year-old female with shortness of breath. She keeps birds for pets Axial CT through the mid lung fields on inspiration, shows diffuse ground glass changes with a combination of mosaic attenuation and normal lung giving the appearance of the head cheese sign.
On the expiration phase the mosaic attenuation remains indicating air trapping and inferring small airway disease
Ashley Davidoff MD TheCommonVein.net 242Lu 13551aL