10 Segmental cervical aplasia in a mare with mosaic X-chromosome aneuploidy

Segmental cervical aplasia is a congenital Müllerian abnormality characterised by the complete or partial failure of cervical development resulting from abnormal fusion of the Müllerian ducts to the urogenital sinus. In the present case report, we describe a congenital segmental cervical aplasia in a Colombian creole mare. The mare was presented to the Animal Reproduction Clinic of Universidad Nacional de Colombia for diagnosis because the external orifice of her cervix was not detected when a uterine lavage was attempted as a therapy for detectable uterine fluid accumulation. The mare had a history of 20-day oestrous cycles confirmed by receptivity to a mature stallion and had no history of natural service or artificial insemination. A complete breeding soundness evaluation of the mare including transrectal palpation, ultrasonography, vaginoscopy, endoscopy, transvaginal aspiration of the uterine fluid and cytogenetic analysis, and an oestrous cycle follow-up were performed. Clinical and ultrasonographic evaluation of the genital tract revealed normal-size ovaries with structures suggestive of regular ovarian activity. Ovulation was confirmed by the formation of a corpus haemorrhagicum followed by a mature corpus luteum in diestrus. In addition, granular free-floating fluid material distending the uterus was detected. Upon vaginal examination, the organ ended in a blind bag with a small papilla with no evident external os cervix. Cytology of the uterine fluid obtained by transvaginal aspiration showed predominant neutrophils with diplococcus bacteria and inflammatory cells compatible with inflammatory content. Cytogenetic analysis of 134 metaphase lymphocytes showed that the mare had an abnormal karyotype [64,XX]/[63,XO]/[65,XXX] with a ratio of 45%, 45%, and 10%, respectively. G- and C-banded analysis was conducted for the X chromosome. Mosaicism of the X chromosome was diagnosed, and the observed congenital segmental cervical aplasia was proposed as the clinical consequence of the mosaicism detected. To our knowledge, this is the first case of this reproductive pathology in a Colombian mare with regular ovarian activity and X chromosome aneuploidy in mosaic form. The cause of the persistently contaminated uterine content in this mare was not clear; it is possible that via the systemic or transcervical route, bacterial contamination could have colonized the uterus, resulting in chronic inflammation and fluid accumulation. This case report demonstrates the importance of performing an adequate routine gynaecological examination in mares to determine their reproductive health. In most cases, the diagnosis of congenital pathologies of the cervix is an incidental finding when performing breeding programs or therapeutic strategies for managing uterine inflammatory conditions. Furthermore, cytogenetic analysis is an important complementary tool for clinical reproductive examination, to accurately identify causes of congenital malformations, and to determine additional causes of reproductive failure in mares.