Uterine leiomyoma, retained fetal cranial bones, and reproductive microbiome analysis in a fallow deer (Dama dama): a case report.

Pathological and microbiological surveillance of wildlife can reveal clinically silent but biologically important reproductive disorders. This case report describes a middle-aged (6-7 years) fallow deer hind (Dama dama) in good body condition, legally culled in Hungary, in which post-mortem examination identified a uterine leiomyoma in the left uterine horn and retained fetal cranial bones in the cranial vagina. To the best of our knowledge, this is the first published description of uterine leiomyoma in this species. Gross pathology, histopathology, and desmin immunohistochemistry supported the diagnosis of leiomyoma, and 16S rRNA amplicon sequencing was used to compare the microbiomes of the unaffected uterine horn, affected uterine tissue, and feces. The affected uterine sample showed a microbial profile more similar to that of feces than the unaffected uterine sample, with an increased relative abundance of genera, including Bacteroides, Escherichia-Shigella, and Turicibacter. As this was a single post-mortem case, no treatment was administered. These findings suggest a possible association between chronic mechanical obstruction, retained fetal material, and marked local microbial alteration, while also illustrating the limitations of causal inference from single-animal microbiome data. This case expands the differential diagnosis of reproductive tract lesions in wild ruminants and highlights the value of integrating pathology with careful microbiome interpretation in wildlife case reports.