Neonatal respiratory distress syndrome is a disease of immaturity. The immature lung is not able to produce sufficient surfactant to prevent collapse of many alveoli. Severe diffuse damage to alveoli causes precipitation of protein ("hyaline membranes") adjacent to many alveolar walls. In infants that survive, paicularly if oxygen was used for therapy, the lungs eventually become heavily fibrotic (misnamed bronchopulmonary dysplasia). Abundant neutrophils would not be seen unless the patient had also developed pneumonia. Fibrosis is a late, not early, feature of respiratory distress syndrome. The air spaces are collapsed, not enlarged, in this condition. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 29. Diseases and Injuries of the Fetus and Newborn. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.