Persistent Müllerian duct syndrome

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Reproductive tract showing presence of testes connected to uterine horn and prostate of an essentially male dog[1]

Persistent Müllerian duct syndrome is an autosomal-recessive genetic disease of dogs characterized by ambiguous gonadal and sex differentiation. It is a rare form of male pseudohermaphroditism where Müllerian duct derivatives are retained in otherwise normal male dogs.

Both male and female dogs can be carriers.

During sexual differentiation of male embryos, the Müllerian ducts fail to regress in males during sexual differentiation as a result of abnormalities in the synthesis or action of anti-Müllerian hormone. Müllerian Inhibiting Substance (anti-Müllerian hormone), plays an important role in mediating regression of the Müllerian ducts, the embryologic precursors of the uterus, Fallopian tubes, and upper vagina. The causes retained rudimentary Müllerian structures or an infantile uterus and Fallopian tubes[2].

A breed predisposition has been noted in the Miniature Schnauzer[3] and Bassett Hound[4]. Affected miniature schnauzers are 78,XY males and have bilateral testes and normal androgen-dependent masculinization of the internal and external genitalia. However, all Müllerian duct derivatives, bilateral oviducts, a complete uterus with cervix and the cranial portion of the vagina, are also present[5].

In dogs, this condition is frequently associated with cryptorchidism (approximately 50% of affected dogs have normally descended testes and are fertile)[6], hypospadias and prostate disease (e.g. deformed or absent prostate)[7].

Affected dogs have normal development of external genitalia, but internally develop fully differentiated Müllerian and Wolffian duct systems.

Common symptoms in older dogs is sertoli cell tumors (in the undescended testis)[8], feminization syndrome, pyometra, recurrent cystitis[9] and infertility.

Most dogs are diagnosed at time of routine neutering and a differential diagnosis would include XX sex reversal.

A DNA test is available for detection of this disorder in dogs[10].

Treatment involves orchidectomy and hysterectomy.

Prevention is limited to the elimination of affected dogs and carriers from the breeding population.

References

  1. Meyers-Wallen VN (2012) Gonadal and sex differentiation abnormalities of dogs and cats. Sex Dev 6(1-3):46-60
  2. Brook CG et al (1973) Familial occurrence of persistent Müllerian structures in otherwise normal males. Br Med J 1:771–773
  3. Breshears MA & Peters JL (2011) Ambiguous genitalia in a fertile, unilaterally cryptorchid male miniature schnauzer dog. Vet Pathol 48(5):1038-1040
  4. Nickel RF et al (1992) Persistent müllerian duct syndrome in the basset hound. Tijdschr Diergeneeskd 117(1):31S
  5. Matsuu A et al (2009) A case of persistent Müllerian duct syndrome with Sertoli cell tumor and hydrometra in a dog. J Vet Med Sci 71:379–381
  6. Meyers-Wallen VN et al (1989) Müllerian inhibiting substance is present in testes of dogs with persistent Müllerian duct syndrome. Biol Reprod 41:881–888
  7. Kuiper H et al (2004) Persistent Mullerian duct syndrome causing male pseudohermaphroditism in a mixed-breed dog. Vet Rec 155:400–401
  8. Vegter AR et al (2008) Persistent Müllerian Duct Syndrome in a miniature schnauzer dog with signs of feminization and a Sertoli cell tumor. Reprod Domest Anim 45(3):447-452
  9. Wu X et al (2009) A single base pair mutation encoding a premature stop codon in the MIS type II receptor is responsible for canine persistent Müllerian duct syndrome. J Androl 30(1):46-56
  10. Pujar S & Meyers-Wallen VN (2009) A molecular diagnostic test for persistent Müllerian duct syndrome in miniature schnauzer dogs. Sex Dev 3(6):326-328