Which of the following would most likely be observed in the lung during an autopsy of a 2-week-old infant who died of neonatal respiratory distress syndrome?
**Core Concept**
Neonatal respiratory distress syndrome (NRDS) is a common condition in preterm infants, characterized by difficulty breathing due to lung immaturity. The underlying pathophysiology involves surfactant deficiency, leading to atelectasis and impaired gas exchange.
**Why the Correct Answer is Right**
Surfactant is a complex mixture of phospholipids and proteins that reduces surface tension in the alveoli, allowing for easier lung expansion during inhalation. In NRDS, surfactant deficiency leads to increased surface tension, resulting in alveolar collapse and atelectasis. Autopsy findings in NRDS would show **hyaline membrane formation** in the alveoli, which is a characteristic feature of this condition. This occurs due to the accumulation of cellular debris, protein, and surfactant in the alveoli, forming a thick, pinkish-gray membrane.
**Why Each Wrong Option is Incorrect**
**Option A:** Pulmonary edema would be a possible finding in conditions like pneumonia or congenital heart disease, but it is not the most characteristic feature of NRDS.
**Option B:** Chylothorax, or the accumulation of lymphatic fluid in the pleural space, is not typically associated with NRDS.
**Option C:** Pneumonia would be a possible co-existing condition, but it is not the primary cause of NRDS.
**Clinical Pearl / High-Yield Fact**
In preterm infants, the risk of NRDS increases with decreasing gestational age, and it is often associated with maternal diabetes, multiple gestations, and maternal respiratory infections.
**Correct Answer: C. Hyaline membrane formation in the alveoli.**