Common Symptoms
Persistent Müllerian duct syndrome (PMDS) is an inherited disorder of sexual development affecting male dogs. In early, In Utero development all canine fetuses have precursors of the uterus, fallopian tubes and upper vagina called Müllerian ducts. In normal male fetuses, the Müllerian ducts regress as sexual differentiation occurs in utero allowing for development of male sexual anatomy. In affected male dogs the female reproductive organs fail to regress in utero. Approximately half of the affected male dogs have externally normal testes and are fertile, but internally have remnants of female reproductive organs, including the uterus. The other 50% of affected male dogs have Cryptorchidism in addition to remnants of female reproductive structures. Cryptorchidism predisposes dogs to infertility and testicular tumors. Affected dogs may also have small testes. Male dogs may need to have a Hysterectomy if the uterus becomes infected. This disorder is limited to expression in males. Females with this condition have normal internal and external female anatomy.
Breed-Specific Information for the Standard Schnauzer
Standard Schnauzer is included as a breed susceptible to persistent müllerian duct syndrome because of its close relatedness to the Miniature Schnauzer breed, which is known to develop this disease due to Mutation of the AMHR2 gene. The frequency of the causal mutation in the general Standard Schnauzer population is unknown.
Testing Tips
Genetic testing of the AMHR2 gene in Standard Schnauzers will reliably determine whether a dog is a genetic Carrier of persistent Müllerian duct syndrome. Persistent Müllerian duct syndrome is inherited in an Autosomal Recessive manner in dogs but only manifests in male dogs. In other words, male dogs must receive two copies of the mutated gene (one from each parent) to develop the disease while female dogs with two copies of the Mutation do not manifest the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same mutation, there is a risk of having affected male pups. Each male pup that is born to this pairing has a 25% chance of inheriting two copies of the mutation and having the disease and both sexes have a 50% chance of inheriting one copy and being a carrier of the AMHR2 gene mutation. Reliable genetic testing is important for determining breeding practices. Because affected males may appear externally normal and still be fertile, genetic testing should be performed before breeding dogs. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Standard Schnauzers that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
-
Wu X, Wan S, Pujar S, Haskins ME, Schlafer DH, Lee MM, Meyers-Wallen VN. 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. 2009 Jan-Feb; 30(1):46-56.
[PubMed: 18723470]
