Aneuploidy is the result of non-disjunction during meiosis and can be associated with clinical signs in the offspring, depending on the chromosomes that are either absent or in excess.
Several cases of aneuploidy have been reported in dogs, and cytogenetic investigations of intersex dogs have revealed cases of XXY trisomy and X monosomy, but only a few cases of X trisomy are described in dogs.
Primary clinical symptoms include a history of estrous cycle abnormalities included persistent anestrus, anovulation, a slow rise in serum progesterone and testosterone concentrations, 'split' heats, insufficient luteal phase and persistent estrus, ovarian cysts, ovarian tumor, endometrial hyperplasia, mucometra, hydrometra, and uterine infection.
Affected bitches also have a higher risk of dental abnormalities such as oligodontia.
Ultrasonography may reval abnormalities within the ovarian or uterine structure but definitive diagnosis requires chromosomal testing.
Histological examination of ovaries during ovariohysterectomy may reveal hypoplastic ovarian tissue with poorly differentiated sex cords and little evidence of primordial or mature follicles.
However, based on incidence studies, it is suspected that the majority of canine trisomy-X cases may escape diagnosis, because accompanying symptoms of reproductive disturbance, skeletal malformations, and behavioral or psychiatric disorders can be so mild that karyotyping is not performed.
Ovariohysterectomy is usually advised in order to limit transmission of the condition vertically to offspring. However, some dogs may be required to be treated and a GnRH agonist, gonadorelin can be given at a dose of 2.2 μg/kg intramuscularly, once daily for 3 days to induce progression in the cycle.
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