Acute Interstitial Pneumonia (Accelerated Interstitial Pneumonia; Hamman-Rich Syndrome) By Joyce Lee, MD, MAS, University of Colorado School of Medicine Reviewed / Revised Jun 2021 | Modified Sep 2022 View Patient Education Diagnosis Treatment Acute interstitial pneumonia (AIP) is a rare and fulminant idiopathic pulmonary disorder that manifests similarly to acute respiratory distress syndrome (ARDS).