Infertility in an American Quarter Horse mare with cervical duplication.

Cervical duplication is a disorder of sexual development (DSD) that may be present in the absence of chromosomal aberrations. It is a rare cause of infertility in mares and is attributed to the failure of the Müllerian ducts to fuse properly, leading to the persistence of the median walls along the whole length of the cervix. This case report involves a 13-year-old American Quarter Horse mare with cervical duplication. Prior to this diagnostic, the mare was bred multiple times, but pregnancy was not achieved. The mare presented for a breeding soundness evaluation. During the examination an aberrant cervical conformation was palpated and further investigated. Cytogenetic analysis and a PCR for the Y-linked SRY gene and the X-linked androgen receptor gene was performed. A normal 64,XX, SRY-negative karyotype was determined. Infertility was associated with cervical abnormality, affecting in some degree uterine clearance causing accumulation of fluid seen on ultrasound.