Primary pulmonary hypoplasia: report of a case with polyhydramnios.

We describe a case of extreme primary pulmonary hypoplasia. No other congenital anomalies and none of the conditions known to be associated with pulmonary hypoplasia were present. Pregnancy had been complicated by substantial polyhydramnios. The hypoplasia was due to a marked deficiency of the respiratory parenchyma in the presence of normal upper airways and bronchi. Virtually no parenchymal development had occurred and there were very few bronchioles, alveolar ducts, and alveoli. The changes differ from those seen in pulmonary hypoplasia secondary to congenital diaphragmatic hernia, bilateral renal agenesis, anomalies of the urinary outflow tracts, and malformations of the thoracic cavity, in which the pulmonary hypoplasia appears to be compressive in nature. While neither the etiology or pathogenesis of the pulmonary hypoplasia are apparent in this case, the presence of substantial polyhydramnios during pregnancy suggests the possibility that the developing lungs may offer an important surface area for reabsorption and recycling of constituents of amniotic fluid.