Male pseudohermaphroditism of the testicular feminizing type in a horse.

The research article investigates a case of pseudohermaphroditism, more specifically testicular feminization (tfm), found in a 7-year-old Quarter Horse. This condition suggests the horse displayed primarily female physical traits but retained male behavioral tendencies.

Identification of Pseudohermaphroditism

• The 7-year-old Quarter Horse in question exhibited what is known as male pseudohermaphroditism or more specifically, the testicular feminization (tfm) syndrome. This is a condition where an individual genetically male displays physical characteristics that are primarily female along with male behavioral attributes.
• The conditions typically associated with tfm were observed in this case. The quarter horse showed female physical traits such as body structure but behaved as a male would.

Anatomical Findings

• The anatomical investigation of the horse showed the presence of testes in the abdomen, a characteristic of a male horse. However, the uterus and cervix, which are strictly female organs, were absent. This reinforces the diagnosis of tfm.
• The horse’s vagina appeared normal in depth but came to an abrupt ending. This is another sign of tfm, showing a reproductive anatomy that is more female than male, but with critical discrepancies.

Chromosomal Determination

• The sex chromosomal composition of the horse was determined to be XY, typical of males, through examination of testicular fibroblasts and leukocyte cultures. This chromosome arrangement underlines the genetic male nature of the individual even though it possesses female physical characteristics.

Family Pedigree Construction

• The researchers went a step further to explore if there was a genetic history of tfm in the horse’s family. This was done by forming a family pedigree. The family pedigree showed a trend of hereditary transmission akin to that seen in other mammalian species with tfm.
• This suggests that the tfm condition in this Quarter Horse is likely inherited, and if other horses from this pedigree were to be examined, similar findings might be reported.