Muellerian ducts (paramesonephric ducts) are small structures that exist in both male and female embryos during the early fetal development, at 35-36 days of gestation, the embryo begins to differentiate into male or female. In the female, Muellerian ducts will develop to form the uterine tubes, uterus, cervix, and the upper one-third of the vagina. In the male, Muellerian ducts are lost because the testes starts producing a hormone that causes regression of the Mullerian ducts.
In Miniature Schnauzer males which are affected by Persistent Müllerian duct syndrome (PMDS), the Müllerian ducts fail to regress during sexual differentiation, and therefore, all Müllerian duct derivatives, bilateral oviducts, a complete uterus with cervix and the cranial portion of the vagina, are also present.
Approximately 50% of affected dogs have normally descended testes and are fertile . However, the remaining 50% have unilateral or bilateral cryptorchidism, and as a result can be infertile and develop testicular tumors.
Treatment involves surgical procedures and significant expenses for dog owners. Prevention is limited to the elimination of affected dogs and carriers from the breeding population. In the miniature schnauzer, PMDS is inherited as an autosomal recessive trait with expression limited to homozygous males. Both males and females can be carriers. However, affected dogs cannot be identified by physical examination alone, particularly if they are not cryptorchid. Similarly, carriers cannot be detected, as they are reproductively normal males or females. A DNA test is now available to identify dogs as clear, carrier or affected.
Females with one or tow copies of the mutation will have normal internal and external female anatomy.
Males with one copy of the mutation will not develop the disease.
About 50% of Males with two copies of the mutation are likley to express the disease.
Avoid breeding carrier to carrier.