Mechanism of the teratogenic effect of thalidomide.

The mechanism of the teratogenic effect of thalidomide is unknown. The hypothesis that this drug acts on the sensory nerves of the embryo was derived from radiological observations of two series of thalidomide-deformed children. Supplementary evidence was found in neurological, embryological and other literature, to support the hypothesis of embryonic neuropathy. The concept can be extended to include visceral as well as skeletal deformities. Evidence for and against the hypothesis is presented, and its application to a broad spectrum of congenital deformities provides an explanation of a number of previously unrelated facts. Areas for further research are suggested.