Disorder of sexual development in which chromosomal males (XY) with normal testes retain Müllerian duct derivatives (uterus, oviducts, uterine horn). It results from a defect in the anti-Müllerian hormone (AMH) pathway or its receptor (AMHR2). A hereditary form has been described in the Miniature Schnauzer.

Miniature Schnauzer: allele frequency of the AMHR2 mutation 0.16 and carrier frequency 0.27 (Smit et al. 2018, n=216). Limited data in other populations.

- Phenotypically normal males with testes
- Presence of uterus/oviducts found at surgery or necropsy
- Risk of uterine torsion or inguinal hernia
- Risk of uterine pathology (infection, neoplasia)
- Possible associated cryptorchidism

PMDS in the Miniature Schnauzer was identified after observing males with testes and retained Müllerian structures. The AMH/AMHR2 pathway was investigated as the cause, since anti-Müllerian hormone is what produces regression of the Müllerian ducts in male sexual development. The exact molecular assignment of the gene/variant (AMH or AMHR2) in the Miniature Schnauzer should be verified in the primary source.

- Genotype AMHR2 in Miniature Schnauzer breeding animals before mating.
- Do not mate carrier×carrier (25 % homozygotes); carrier×clear does not produce affected animals and gives 50 % carriers.
- Affected males with a scrotal testis may be fertile: do not breed affected animals or mate carriers with each other.
- Orchiectomy and hysterectomy in affected males (risk of Sertoli cell tumour and pyometra).
- Homozygous females are healthy but transmit the mutation to all offspring.

The diagnosis may be incidental at surgery (castration, herniorrhaphy) or on imaging (ultrasound). The differential diagnosis includes other disorders of sexual development (true hermaphroditism, 46,XY disorders of sexual development). Karyotyping and determination of AMH/testosterone are helpful. Confirm with a genetic test for the variant if available. Affected males may have variable fertility depending on the degree of cryptorchidism or associated testicular pathology.

1. Wu X et al. 2009, mutación de un par de bases que codifica un codón de parada prematuro en el receptor MIS tipo II, responsable del síndrome del conducto mülleriano persistente canino (PMID 18723470)
2. Pujar S, Meyers-Wallen VN. 2009, test de diagnóstico molecular para el síndrome del conducto mülleriano persistente en Schnauzer miniatura (PMID 20051676)
3. Smit MM et al. 2018, prevalencia de la mutación AMHR2 en Schnauzer miniatura (PMID 29194807)
4. OMIA:002775 PMDS (AMHR2)