Caudal duplication syndrome: a literature review and reappraisal of its pathoembryogenesis.

We propose a theory that by a molecular interaction, an insult causes late gastrulation phase problems, resulting in ectopic primitive streak formation, and therefore, a duplication of the CCM is induced. Subsequently, the overactivity of abnormally positioned midline mesenchyme between the two CCMs may divide the hindgut derivatives by a central septum. Underactive lateral and caudal pushes of the caudal mesenchyme may lead to an association of features shown in caudal agenesis.