A study of cartilage development in pulmonary hypoplasia.

To discriminate between different forms of pulmonary hypoplasia (PH), 24 hypoplastic lungs were studied for their development of bronchial cartilage plates and peripheral air spaces. In 6 lungs from premature infants with oligohydramnios, normal amounts of immature and irregularly shaped cartilages were distributed with mitoses concentrated toward the periphery of the bronchi. Pulmonary acini appeared markedly immature. In 5 lungs from infants with diaphragmatic hernia, large numbers of cartilage bars were clustered around the proximal bronchi, whose branching was much reduced. Peripheral air spaces were small but structurally mature. In Potter syndrome, small amounts of tiny, mature cartilages were observed irregularly around the proximal bronchi and poorly distributed into the peripheral bronchi. The acinar structure was very immature. In 4 anencephalic infants, a marked decrease in the volume of mature cartilage was present, with cartilage seen only around proximal bronchi; the acini were atelectatic and less well developed. It is suggested that the earlier the action of a teratogen, the greater the abnormality of bronchial branching, cartilage distribution, and later lung development.