Pulmonary hypoplasia resulting from phrenic nerve agenesis and diaphragmatic amyoplasia.

We report the clinical, general postmortem, and pulmonary morphometric features of a unique case of pulmonary hypoplasia resulting from phrenic nerve agenesis and diaphragmatic amyoplasia. The lungs showed a marked reduction in the number of bronchial branches with relatively normal intra-acinar growth, indicating interference with lung development before the sixteenth week of gestation. The pulmonary abnormalities arose early in gestation, suggesting that normal diaphragmatic neuromuscular development is essential for maintaining thoracic volume and permitting lung growth even before the fetus is capable of regular respiratory movements. The infant also had remodeling of the pulmonary circulation, causing persistent pulmonary hypertension. This case clarifies the interrelationship of diaphragmatic innervation, thoracic volume, fetal respiration, and lung development.