Which two malformations are cited as leading to pulmonary hypoplasia and increased risk of persistent pulmonary hypertension?

• A. Tracheoesophageal fistula and pulmonary sequestration
• B. Patent ductus arteriosus and bronchopulmonary dysplasia
• C. Congenital diaphragmatic hernia and congenital cystic adenomatoid malformation
• D. Pulmonary hypoplasia is not associated with these

Answer: (C)

Pulmonary hypoplasia occurs when lung development is interrupted, often because space in the chest is occupied or growth is otherwise distorted during fetal life. Congenital diaphragmatic hernia allows abdominal contents to herniate into the thorax, physically crowding developing lungs and restricting growth, which leads to underdeveloped pulmonary vasculature. This underdevelopment means the pulmonary vascular resistance remains high after birth, increasing the risk of persistent pulmonary hypertension. A congenital cystic adenomatoid malformation acts as a mass within the lung that disrupts normal lung growth and function, also causing hypoplasia of the affected lung and abnormal pulmonary vasculature, with a similar heightened risk of PPHN after birth. Together, these two malformations are classically cited as leading to pulmonary hypoplasia and elevated risk of persistent pulmonary hypertension.

Other options don’t fit as well because they involve conditions that are less directly tied to developmental undergrowth of the lungs or to the same pattern of neonatal pulmonary vascular disease. Tracheoesophageal fistula and pulmonary sequestration can cause respiratory distress from abnormalities in airway or blood supply, but they are not the classic congenital malformations most associated with pulmonary hypoplasia and PPHN. Patent ductus arteriosus and bronchopulmonary dysplasia are neonatal issues related to postnatal circulatory changes and lung injury, not congenital causes of hypoplasia with PPHN.