Retinoid-induced nasal malformations.

Treatment of pregnant Sprague-Dawley rats with etretinate or retinoic acid on pregnancy days 8.5-9.0 resulted in craniofacial defects in all embryos. A morphological investigation of the malformations occurring in the nasal region is described. The external nose was deformed with a depressed nasal bridge and pronounced hump. Fusion between nasal processes was defective, resulting in fistulas and clefts. The nasal septal cartilage was reduced in size, the paranasal cartilage was missing, the parietothecal cartilage was deformed and the paraseptal cartilage was dislocated. Aberrant vessels were seen on the external nose in combination with underdevelopment of the vibrissae. The distance between the outer nasal pores was reduced after administration of retinoids.