[Adenomatous hyperplasia of equine allantoic epithelium - a warning sign? - A case report].

Adenomatous hyperplasia of the equine allantoic epithelium (EAAH) is an infrequently observed nodular or plaque-like change in the placenta of the mare which is presented as a case description. EAAH is most frequently diagnosed in cases of aborted fetuses and is associated with inflammatory changes of the placenta. Histologically, different degrees of EAAH may be distinguished; however, these are not associated with specific clinical signs, degree of inflammation, a particular pathogen, or the frequency of abortions. It is assumed that EAAH represents a secondary, reactive change and has per se no influence on the vitality of the fetus itself. The lesion, however, should be taken seriously and considered as a warning sign for possible previous subclinical infections, even in clinically normal foals. This in turn should prompt more detailed clinical examination and monitoring of the mare and foal.