A case of true hermaphrodism in a horse

anglais. peer reviewed

anglais. True hermaphroditism in horses, is a complex and poorly under- stood disorder of sexual development characterized by the presence of both male and female gonads as separate organs or in a combined structure called ovotestis. A 3-year-old Spanish nullipa- rous mare with a history of stallion behaviour and an abnormal reproductive exam was presented at the Equine Clinic of the University of Li ege. Externally, a small vulva with an enlarged clitoris was observed. Transrectal ultrasonography showed a thin (<1 cm) uterus, leading to a small heterogeneous structure in the normal place of the left ovary. No structure could be identified in the presumed location of the right ovary. Speculum exam was compatible with a vaginal agenesis, as the cervix opened craniad the urethral meatus. Oestradiol, progesterone and testosterone concen- trations were compatible with a stallion’s endocrinology. Gonads were laparoscopically found in the usual location of the ovaries in both flanks and excised. Histopathology of both gonads showed atrophic testicular tissue with hyperplastic Leydig cells. The left gonad also contained ovarian tissue with some scarce primordial follicles. Clitoral enlargement is the first symptom most commonly identified in animals with true hermaphroditism and can be explained by the production of testosterone by the gonads, however, the aetiology of the vaginal agenesis is unknown. True hermaph- roditism in horses is generally related to 64XX syndrome with or without SRY gene translocation (impending karyotyping analysis). After 5 days the mare was discharged from the clinic, and in absence of testosterone the stallion behaviour disappeared in a couple of months.