DISORDER OF SEXUAL DEVELOPMENT IN A FRIESIAN HORSE

In horses, several presentations of abnormal external genitalia have been described. Disorders of Sex development are associated with an atypical sexual phenotype or cases of intersexuality [1]. Individuals showing atypical sex conditions have been classified according to the gonadal tissue as true hermaphrodites, male pseudohermaphrodites, female pseudohermaphrodites [2]. Genetically they fall into 4 broad categories: XX karyotype, SRY -negative genotype with ovotestis or testis; XY, SRY-negative with gonadal dysgenesis; and XY, SRY -positive with testis or gonadal dysgenesis [2]. The present abstract describes the clinical case of a 3-years-old Friesian horse referred to male-like behavior (nervous temperament, masculine attitude) and ambiguous external genitalia (female phenotype, but anatomical abnormalities of external genitalia). Clinical examination of the external genitalia showed a penis-like structure protruding out of the vulvar region for 8 cm with a cranio-caudad direction. At the inguinal level, mammary development was compatible with the reproductive status of a nulliparous mare, and showed in the intermammary sulcus, a skin lump similar to the penis sheath. Any parenchymatous structures were found with palpation of the external inguinal. Transrettal palpation and ultrasound examination identified aplasia of the body of the uterus and of ovaries. Moreover, the ultrasonographic exam showed segmental hypoplasia of the uterine horns. Laparoscopy through a bilateral flank approach allowed the localization of both gonads and their adnexa into the internal inguinal ring, their dissection, and removal [3]. At the pelvic inlet, a sacculated structure compatible with an aplastic uterus was appreciated. A urethrocistoscopy was performed with a 0.9 mm flexible endoscope. On the floor of the pelvis a masculine urethral opening leads to the urinary bladder through a short urethra. Dorsal to this finding, two sacculated structures were present, a smaller one on the left hand side of the pelvis, a large one on the midline. This structures are similar to the hypoplastic uterine horns. The endocrine function of the gonads was evaluated using the hCG-stimulation test [4]. Blood testosterone concentrations and histological examination of the tissue removed will confirm the type of tissue. Moreover, the cytogenetic and molecolar analysis will show the karyotype and would allow a genetic classification. Disorder of sex development in horses has both genetic and phenotypic heterogeneity as occurs in other species [2]. The degree of genetic modification, its site, and the time of onset are resposible of the high phenotipical variability of the intersex [3].