An infant born at 29 weeks of gestation develops grunting, nasal flaring, and cyanosis within hours of birth. Chest radiograph shows diffuse fine granular opacities with air bronchograms. The fundamental abnormality is:

• A Aspiration of amniotic fluid containing meconium
• B Deficient pulmonary surfactant from immature type II pneumocytes ✓
• C Persistent failure of ductus arteriosus closure
• D Congenital absence of type I pneumocytes

Explanation

Neonatal respiratory distress syndrome results from deficient surfactant synthesis by insufficiently mature type II pneumocytes. Surfactant reduces surface tension, so its lack causes widespread alveolar collapse, atelectasis, and formation of eosinophilic hyaline membranes lining the ducts and alveoli. Risk rises with prematurity, maternal diabetes, and cesarean delivery, and risk falls with antenatal corticosteroids. Meconium aspiration occurs in term or post-term infants, and patent ductus arteriosus is a consequence rather than a cause of the syndrome.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.