A novel embryogenetic mechanism for Currarino's triad: inadequate dorsoventral separation of the caudal eminence from hindgut endoderm.

Currarino's triad is a congenital malformation involving the combination of anorectal stenosis, a presacral mass (most often a teratoma or ventral menigocele) and an anterior sacral bony defect (scimitar sacrum). Current theories regarding its embryogenesis are difficult to reconcile with our current understanding of caudal neuraxial and hindgut development. Caudal neuraxial structures develop from the caudal eminence (or tail bud), which normally separates from the hindgut endoderm concurrent with ingrowth of the posterior notochord during late gastrulation. We describe the first reported association of Currarino's triad with a caudal split cord malformation. It has previously been proposed that split cord malformations and related 'complex dysraphic malformations' involving abnormalities of one or more of the three primary germ layers arise through disordered midline axial integration during gastrulation. The presence of a split cord malformation in a patient with Currarino's triad suggests that the two disorders share a common embryogenetic pathway. We propose that the malformations of Currarino's triad arise through a failure of dorsoventral separation of the caudal eminence from the hindgut endoderm during late gastrulation.