Urogenital Hypoplasia and X Chromosome Monosomy in a Draft Horse Filly.

This case study is about a 5-month old draft horse filly suffering from urinary incontinence and severe perivulvar dermatitis, and how researchers found an abnormality in her X chromosome along with a misplaced left ureter.

Background of the Case

• The 5-month-old horse had been facing issues with incontinence and excessive inflammation around the vulvar area over the last two months.

Preliminary Investigations

• Initial vaginal endoscopy revealed a misplaced left ureter entering the rear part of the vaginal lumen.
• Apart from this, the cervix showed signs of underdevelopment, and urine was accumulating in the uterus.

Intervention

• A surgery (left ureter-nephrectomy) was performed under general anesthesia to remove the misplaced ureter and kidney.
• In addition, a cytogenetic examination was also carried out to study the filly’s chromosomes.

Cytogenetic Findings

• The study revealed a chromosomal abnormality, XO monosomy, combined with a mosaic of 63,X/64,XX. XO monosomy is an abnormal condition that results from the loss of one of the sex chromosomes.
• This resulted in the horse having only one X sex chromosome in some cells (63,X), while having two Xs – a normal condition – in others (64,XX). This inconsistency of chromosome count in different cells is referred to as a mosaic pattern.
• This is the first reported instance of a chromosome abnormality in a draft horse filly combined with a misplaced left ureter.

Recommendations

• Based on the outcome of this case, researchers recommend a cytogenetic evaluation for any female horse presenting developmental abnormalities in cervix, uterus, ovaries, or irregularities in their estrous cycle.