Osseous metaplasia

Osseous metaplasia is a rare condition in which there is a transformation of the

normal endometrial tissue into bone. It is an uncommon clinical finding with an

incidence of 0,3/1000 and most cases occur after miscarriage or abortion. The

presence of bone in the endometrium was first described by Virchow who related this

condition to a spontaneous differentiation of fibroblasts into osteoblasts. Typically, this

type of metaplasia occurs during reproductive years and more than 80% of reported

cases ocurr after pregnancy.

There are two main theories to explain the existence of bone fragments in the

endometrial tissue. The one by Thaler, who relate this entity to retention of osseous

fetal parts after abortion or miscarriage after 12 weeks of pregnancy. This first theory

cannot explain cases that occurr in patients without previous pregnancies. The second

theory is that of a true endometrial osseous metaplasia, in which there is a osseus

transformation of the endometrial stromal cells, this metaplasia is consequence of

irritative, toxic or hormonal stimuli. Probably both theories are right, with cases of true

metaplasia and cases in which retained bones, causes an endometrial inflammation

which leads to a secondary osseous metaplasia.