[An autopsy case of acute interstitial pneumonia].

An autopsy case of a 77-year-old male with acute interstitial pneumonia (AIP) is reported. The patient died of respiratory failure in the extremely rapid course of 8 days. The histogenesis of the thickening of the alveolar wall and the intraluminal lesions were noticed. Incorporation of the hyaline membrane as well as the intraseptal edema and septal cell proliferation played an important role in the fibrous thickening of the alveolar wall. The intraluminal granulation tissue was observed in the alveolar space and the alveolar duct, often extending into the respiratory bronchioles. Intraluminal granulation tissues in the alveoli frequently had the appearance of intraluminal buds of mesenchymal cells, so-called Masson's bodies, and there was little remodeling of pulmonary structures in this case. These findings suggest an acute, diffuse and severe damage of the peripheral respiratory tract and are consistent with bronchiolitis obliterans with classical interstitial pneumonia (BIP) by Liebow and AIP by Katzenstein. This patient had suffered from suspected "Bronchiolitis obliterans organizing pneumonia" (BOOP) one and half years ago. The relationship between AIP, BIP and BOOP is discussed.