Chronic Hypersensitivity Pneumonia. What the Clinical Radiologist Participating in a Multidisciplinary Meet Needs to Know

Chronic hypersensitivity pneumonia (CHP) is a diffuse interstitial lung disease, brought about by an inflammatory response to various known and unknown antigens. It affects the small airways, its surrounding parenchyma and interstitium. It can manifest either as a fibrosing or non-fibrosing diffuse lung disease. The fibrotic pattern is irreversible, hence if not recognized early, it embarks on a downhill course. The pattern and anatomical distribution of fibrosis shows some differences from other fibrosing disorders. Features resembling sarcoidosis, fibrosing NSIP or UIP may be seen towards the end stage, making distinction difficult. Clinical evaluation and perusal of previous records helps suggest the diagnosis and assess its progress. In this review article, an attempt will be made to understand the disease in order to enable the radiologist add value in a multidisciplinary discussion (MDD).