Persistent Müllerian Duct Syndrome (PMDS) in Male Dog & Cat
Persistent Müllerian duct syndrome (PMDS), also known as persistent oviduct syndrome, is a disorder of sexual development in which the uterus and other parts of the female reproductive tract develop in male dogs. The embryo of a developing fetus is predestined to have a female reproductive tract, which includes the mullerian duct. Without proper stimulation by hormones, dogs that develop into males may retain the mullerian duct, which leads to PMDS. With PMDS, male dogs will have normal male external genitalia, but may have unilateral or bilateral undescended testes (cryptorchidism). Persistent Müllerian Duct Syndrome (PMDS) is a disorder of sexual development characterized by the retention of Müllerian duct derivatives—such as the uterus and fallopian tubes—in otherwise phenotypically normal males. While PMDS is well-documented in humans and certain dog breeds, it is relatively rare in cats. However, cases have been reported, particularly among Persian cats.
External genitilia in male puppies with PMDS can appear normal, as the majority of the developmental abnormalities are internal. However, approximately 50% of these males will have cryptorchidism, with a higher likelihood of developing testicular tumors or twisting of the reproductive cords (torsion). Testosterone levels will be normal, but these dogs may be infertile as the temperature of the testes is too high for sperm development. Affected dogs may experience uterine lining inflammation (endometritis) or other complications related to the uterus. Clinical signs may include swelling of the abdomen.
Pathophysiology
During typical male embryonic development, the Müllerian ducts regress under the influence of anti-Müllerian hormone (AMH) produced by Sertoli cells in the testes. In PMDS, this regression fails due to either insufficient AMH production or insensitivity of the target tissues to AMH. Consequently, structures such as the uterus, fallopian tubes, and upper vagina persist alongside normal male reproductive organs.
Clinical Presentation in Cats
Male cats with PMDS usually present with typical male external genitalia and a normal male karyotype (XY). However, they also possess internal female reproductive structures. A notable clinical manifestation is cryptorchidism (undescended testes), which occurs in approximately 50% of affected individuals and can lead to infertility and an increased risk of testicular tumors.
How is it diagnosed
A veterinarian will conduct a thorough exam, including a review of health history and any clinical signs. PMDS is typically first noticed during the neutering process, where it becomes apparent that the testes are not present externally. An ultrasound can determine if there is cryptorchidism (testicular retention). Genetic testing is necessary to determine if there is an underlying genetic cause, which can assist veterinarians with diagnosis and help breeders identify affected and carrier dogs.
Diagnosis of PMDS in cats involves a combination of clinical examination, imaging studies, and genetic testing:
- Clinical Examination: Identifying signs such as cryptorchidism or inguinal hernias may raise suspicion.
- Imaging Studies: Ultrasound or MRI can detect the presence of Müllerian duct structures within the abdomen or pelvis.
- Genetic Testing: Molecular analyses of the AMH and AMHR2 genes are conducted to identify potential mutations. However, studies have shown that not all cases of PMDS in cats are linked to mutations in these genes, indicating the involvement of other genetic factors.
Management and Prognosis
Management strategies for PMDS in cats focus on addressing associated complications:
- Surgical Intervention: Cryptorchid testes are typically removed to reduce the risk of neoplasia. Additionally, removal of persistent Müllerian structures may be considered to prevent potential complications such as infections or neoplastic transformation.
- Monitoring: Regular follow-ups are essential to monitor for any long-term complications.
The prognosis for cats with PMDS is generally favorable, especially when managed appropriately. However, fertility is often compromised, particularly in cases with bilateral cryptorchidism.
Conclusion
PMDS, though rare in cats, represents a unique disorder of sexual development that necessitates awareness among veterinarians. Early recognition and appropriate management are crucial to ensure the well-being of affected cats and to mitigate potential health risks associated with the syndrome.
