Abstract

Acute interstitial pneumonia is a fulminant disease of unknown etiology that usually occurs in a previously healthy person and produces the histologic findings of the organizing phase of diffuse alveolar damage. We experienced an autopsy case of acute interstitial pneumonia of unknown etiology. The patient was a 48 year old man who had been healthy and had not been exposed to organic dusts or other toxic materials. The chief complaints represented were dyspnea and a dry cough for several weeks before hospitalization, and the chest radiographs showed bilateral interstitial infiltrates. Patchy consolidation of air space was also identified and ground-glass attenuation similar to those described in ARDS was detected on high-resolution computed tomography. Steroid pulse therapy, mechanical ventilation, and antibiotics for superimposed bacterial infection were performed, but the symptoms did not improve and the patient died of generalized respiratory insufficiency and severe hypoxemia 2 1/2 months after hospitalization. At autopsy the macroscopic and microscopic findings were confined mainly to the lungs. On the whole, both lungs were firm in consistency and the external surface showed a cobblestone appearance. The cut surface showed almost complete replacement of the normal lung parenchyma with gray to yellow fibrous tissue with a little residual functional area remaining. The pathology of both open lung biopsy and autopsy tissue showed marked hyperplasia of type II pneumocytes, hyaline membrane formation, thickening of the alveolar wall due to extensive fibroblast proliferation, and relatively abundant young collagen deposition in the interstitium. An immunohistochemical stain for cytokeratin revealed epithelial hyperplasia and showed that the alveolar spaces were markedly shrunken by fibrous tissue.

• Keywords: Interstitial pneumonia;Acute;Hamman-Rich Syndrome;Autopsy;