Pathogenesis of Early-Onset Endometriosis

Three main theories have been put forward to explain the pathogenesis of endometriosis, that of a retrograde menstrual transplantation, that of an induction of endometrial cells, and that of an in situ development. These hypotheses belong to two main groups: those proposing that implants originate from the endometrium and those advocating an origin from extra-uterine tissues. More recently, the discovery that stem/progenitor cells from bone marrow can differentiate into endometrial cells suggests a novel pathway through which these cells may colonize peritoneal and extra-peritoneal organs and differentiate into ectopic endometrium. On the other hand, for early-onset endometriosis a different pathogenetic mechanism may be in place. The possibility exists that in neonates endometrial
cells and stroma are retrogradely disseminated in the pelvis, thanks to the presence of uterine bleeding, either visible or occult. Since menstrual desquamation causing neonatal bleeding may contain endometrial stem cells, they may in turn be responsible, through a variety of mechanisms, for early onset endometriosis.