The Mayer-Rokitansky-Küster syndrome. An analysis of its morphology and embryology. Part II: Embryology.

The Müllerian duct (MD; ductus paramesonephricus) develops independent of the coelomic epithelium above the mesonephros. This part of the duct gives rise to the infundibulum with its fimbriated ostium abdominale. The part of the duct which lies along the mesonephros as far as its caudal pole makes a contribution to the ampulla and less often the isthmus. In the area of the mesonephros the MD fuses with the Wolffian duct (WD; ductus mesonephricus). The WD gives rise to the ampulla and the isthmus. Below the caudal pole of the mesonephros, as well as beyond the attachment point of the inguinal ligament of the mesonephros, the later round ligament of the uterus, the MD develops as an outgrowth of the WD and no longer as an independent structure. The MRK syndrome is, in its formal genesis, a non-fusion of the MD with the WD. This explains the fact that in a classic case of MRK syndrome, the Fallopian tube with a very small part of the cornu uteri extends only as far as the connection with the round ligament of the uterus. Different possibilities for the origin of MRK syndrome are discussed. It is suggested that the cause of the development of MRK syndrome could be a deficiency of gestagen and/or oestrogen receptors. This would also explain the various forms of the rudimentary vagina.