At 6 hours of age, an infant male born at 34 weeks gestation developed respiratory distress which persisted and increased in severity despite vigorous treatment with oxygen therapy and ventilation. He developed an intraventricular hemorrhage and died at age 2 days. The solid, red-brown, fleshy lungs had little aeration and a few petechiae on the pleural surfaces. Within each lobule, collapsed air spaces are surrounded by expanded respiratory bronchioles and alveolar ducts lined by eosinophilic hyaline membranes. The epithelium is preserved in the larger bronchi but denuded in many of the small bronchioles.
Isolated membranes contain pyknotic nuclei.
Focally, the collapsed air spaces contain a small amount of cellular debris and fresh hemorrhage and some have a persistent cuboidal epithelium. The lobular septa contain dilated blood vessels and lymphatics. The small muscular arteries have a prominent medial layer. The characteristic features are the combination of hyaline membranes and atelectasis in a prematurely born infant. The infant progressively deteriorated and expired at age 13 days.