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Discussion on PseudoHermaprhodite Mare?
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Member:
ddoregon
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Posted on Monday, Jul 11, 2016 - 3:50 pm:
Got in a rescue arab mare, and was bathing her. Noticed her vulva was a bit odd, and on closer inspection, did not appear diseased, swollen or problematic, just weird. Googled a LOT on the internet, and found images that look just like her vulva.. and they are pseudo hermaphroditic mares! meaning, actually, she would be a stallion. So, is there a test like a dna test or ?? I can have done to determine her actual sex? We don't have any "real" horse vets here, I would have to haul her 200 miles one way to be palpated. I was hoping a simple blood test that could be done/sent in with directions by the vet, or maybe Texas AM does it? I will post a photo shortly of her vulva. Here is OTHER horses with the condition. 
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Member:
ddoregon
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Posted on Monday, Jul 11, 2016 - 4:39 pm:
Here is Luna's vulva. Looks like testicles above, that familiar wrinkle LOL! Its a little cruddy, she's not keen on anyone back there. Again, this mare is a rescue I know nothing other than she was starved nearly to death, and now I have her ;o).
*** I will also note, upon reading about this condition that most of these mare/stallions act horribly, stallionlike, however this mare is a docile doll. NO aggression toward other horses, people or anything at all. So maybe she just has the external partial genitalia but no testes? She is 8 years old, so I am sure she would be behaving like a stallion by now, if she was going to do so.
It will be very interesting to see how to present this for resale.. Mare/stallion..????? 
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Moderator:
DrO
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Posted on Tuesday, Jul 12, 2016 - 10:02 am:
Hello DD,
Not only are chromosomal abnormalities possible, certain tumors in mares can release male sex hormones (see Granulosa Cell Tumors), and some issues with mares displaying signs of male like phenotype or behavior remain unexplained other than elevated testosteone levels. Behavior can be an important marker but it is not absolute. Here is a article that demonstrates the range of possibilities on some abnormalities seen. Note that SRY (below) is a gene on the Y chromosome necessary for the development of the testis. Contact your vet for recommendations on where to send the blood:
Equine disorders of sexual development in 17 mares including XX, SRY-negative, XY, SRY-negative and XY, SRY-positive genotypes.Sex Dev. 2011;5(1):16-25. doi: 10.1159/000322811. Epub 2010 Dec 22.
Villagómez DA1, Lear TL, Chenier T, Lee S, McGee RB, Cahill J, Foster RA, Reyes E, St John E, King WA.
Author information
Abstract
We described the clinical, cytogenetic and molecular findings of 17 clinical equine cases presented for abnormal sexual development and infertility. Six horses with an enlarged clitoris had an XX, SRY-negative genotype, which displayed male-like behavior (adult individuals). Bilateral ovotestes were noted in 2 of those cases, while another case showed increased levels of circulating testosterone. Six horses with a female phenotype, including normal external genitalia, had an XY, SRY-negative genotype. These individuals had small gonads and an underdeveloped internal reproductive tract. Four horses with normal appearing external genitalia had an XY, SRY-positive genotype, 3 of them had hypoplastic testes and male-like behavior. In addition, one young filly with enlarged clitoris and hypoplastic testes had the same genotype but did not show male-like behavior due to her age. Three of these horses were related with 2 being siblings. These findings demonstrate the diversity of disorders of sexual development seen in the horse. Furthermore, they emphasize the need for further research to identify genes involved in abnormal sex determination and differentiation in the horse.
If you are not having any related problems nor considering breeding I am not sure the point of testing but I would begin with sex hormone assays, again see the granulosa cell tumor article.
DrO
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Member:
ddoregon
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Posted on Tuesday, Jul 12, 2016 - 2:07 pm:
Thanks Dr O. I guess for ME it would be, if she is really a he or ? I dunno. She acts like a she though. No cresty neck, no bad behavior.. On the granulosa tumor, I have another mare (what are the chances lol) that DOES act like a stud. Huge muscles, mouthy, bratty, etc. I must be a magnet for these mares LOL! Thank you for your reply, I do not plan to breed her or anything other than make her happy ;o)
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