Skeletal malformations associated with congenital diaphragmatic hernia: experimental and human studies

Skeletal malformations are seen occasionally in infants with congenital diaphragmatic hernia (CDH). This study examines whether nitrofen, able to produce CDH in fetal rats, also induces skeletal anomalies and, if so, whether these are similar to those seen in CDH patients.

Pregnant rats received either nitrofen (100 mg, n = 7) or no treatment (n = 2) on gestational day 9.5. Skeletal anatomy was studied in fetuses recovered on day 21 after alcian blue-alizarin red staining. The charts and postmortem records of 117 stillborns or newborns who died of CDH were investigated retrospectively for skeletal defects. The proportions of anomalies found in the different groups were compared.

The 15 control rat fetuses were normal, whereas 57 of 90 nitrofen-exposed animals (63%) had CDH accompanied by other malformations. Skeletal defects limited to vertebral segmentation or identity anomalies (split vertebra or absent, hypoplastic, or fused ribs) were seen at low thoracic and high lumbar levels in 68% of animals with CDH and in 57% of those without. Delayed ossification of limbs was seen in treated animals. There were skeletal malformations in 31.6% of the 117 human patients with CDH. Costovertebral defects (malformed, extra or defective vertebral bodies or ribs and spina bifida) were comparably frequent in infants with syndromes and in those without them (31.2% v 17.8%, not significant), whereas limb defects were significantly more frequent in those with syndromes (56.2% v 13.9%, P<.05).

The nature and location of costovertebral malformations found in both CDH patients and nitrofen-exposed rats suggest that the diaphragmatic defect and the associated organ malformations might be caused by the same early embryonal disturbance involving axial and para-axial mesoderm.