LORI.canine

A true intersex (hermaphrodite) dog

Keywords: intersex, DSD, true, hermaphrodite, canine, dog, nomenclature

This entry relates to a dog presumed to be female when it was born. At ten months of age, the animal experienced discomfort due to abrasion of a penis-like mass protruding from the vulva lips. The mass, and two intra-abdominal gonads were removed surgically. No tissue was available from the tubular reproductive tract and its anatomy was not described. The author only had access to cut and stained histological sections of the gonads. Also, the history did not state which gonad had been sampled histologically or if both gonads had been similarly affected.

In the histology of gonad seen here, seminiferous tubules devoid of active spermatogenesis can be seen at upper left. Only sertoli cells were present in these tubules. In the same inset image, a large tertiary (graafian) follicle is seen. In the smaller inset image at lower magnification, seminiferous tubules are seen again, adjacent to a group of cortical follicles in various stages of development.

Image size: 2113 x 1321 px

This polyovular follicle and several others were seen in this gonad. Polyovular follicles are common in normal dogs and cats. Up to seven oocytes have been seen in a single follicle. 

Image size 1431 x 864 px

Discussion.
If both gonads had contained male and female elements in this patient (most likely) it would be referred to as a bilateral, true hermaphrodite. If only one gonad was affected, the term lateral true hermaphrodite would have been used. Usually the rest of the genital tract is ambiguous in true hermaphrodites.

It should be noted that the terms "hermaphrodite" and "sex-reversed" are being discarded (especially in human medicine) in favor of less offensive, more modern and descriptive nomenclature. New terminology falls under the umbrella of "Disorders of  sexual development" (DSDs) with specific annotations pertaining to the condition added after DSD. In this case for example, the animal would be referred to as having a DSD with bilateral ovotestes and ambiguous genitalia. If the karyotype and SRY status were known, they would be added to the description. The author acknowledges the value of these changes but believes that the terms hermaphrodite and pseudohermaphrodite (pseudo-hermaphrodite) are valuable descriptors and should not be abandoned in veterinary medicine. At risk of reprimand, their use continues in this entry.

True hermaphroditism is occasionally seen in humans and of course, in many animals as well, including wild species. The author encountered a report of true hermaphroditism in a Beluga whale; all the more interesting because the ovarian and testis elements were separate from one another and that situation occurred bilaterally.

Most cases of true hermaphroditism in humans and dogs are associated with XX karyotypes. In some of these, translocated SRY sequences occur on the X chromosome or elsewhere, explaining the presence of testes tissue. In most cases however, the SRY sequence is absent. It is presumed that testes determining pathways distal to SRY must be active in such cases. In true hermaphrodites with XY karyotypes, defects in the SRY gene have been detected. As expected, where mutations of the SRY sequence were severe, no testes tissue developed at all. Those individuals developed ostensibly normal ovaries.

The true hermaphrodite condition is complex and still poorly understood. Just how complex and intriguing, is illustrated by a case of an American Cocker Spaniel with ovotestes and a normal 78, XX karyotype (Seldon et al, 1978). Despite the presence of ovotestes, this animal had given birth to three pups. One was dead and not karyotyped. Of the remaining two pups, one was an apparently normal 78,XX female and the other, a unilaterally cryptorchid male with an ambiguous genital tract and a 78, XX karyotype.

Selected references.

Braun, A. 1993. True hermaphroditism in a 46,XY individual, caused by a postzygotic somatic point mutation in the male gonadal sex-determining locus (SRY) :molecular genetics and histological findings in a sporadic case. Am.J. Hum. Genet. 52:578-585

De Guise, S. et al. 1994. True Hermaphroditism in a St. Lawrence Beluga Whale (Delphinapterus leucas). J. Wildlife Diseases.30:287-290.

Dreger, A.D.et al. 2005. Changing the nomenclature/toxonomy for intersex\; a scientific and clinical rationale. J. Pediatric Endocrinol. Metab. 18:729-733

Hubler, M. et al. 1999. Sry-negative XX true hermaphrodite in a basset hound. Theriogenology. 51:1391-1403

Kousta, E. et al. 2010. Sex determination and disorders of sex development according to the revised nomenclature and classification in 46,XX individuals. Hormones. 9:218-231

McElreavey, K. et al. 1992. A minority of 46,XX true hermaphrodites are positive for the Y-DNA sequence including SRY. Human genetics. 90:121-125

Meyers-Wallen, V.N. et al. 1997. Sry-negative XX true hermaphroditism in a Pasa Fino horse. Equine Vet J. 29:404-408

Meyers-Wallen, V.N. 2006. Genetics, genomics, and molecular biology of sex determination in small animals. Theriogenology. 66:1655–1658

Meyers-Wallen, V.N. 2009. Review and Update: Genomic and Molecular Advances in Sex Determination and Differentiation in Small Animals. Reprod.Dom.Anim. 44:40–46

Pérez-Gutiérrez, J.F. 2015. Bilateral Ovotestes in a 78, XX SRY-Negative Beagle Dog. J. Am. Anim. Hosp. Assoc. 51:267– 271

Selden, J.R. et al 1978. Genetic Basis of XX Male Syndrome and XX True Hermaphroditism: Evidence in the Dog. Science, 201: 644-646

Sommer, M.M  and Meyers-Wallen, V.N. 1991 XX true hermaphroditism in a dog.  J. Am. Vet. Med. Assoc. 198:435-438