Persistent Müllerian duct syndrome is an XY disorder of sexual development described in dogs, particularly in Miniature Schnauzers, and is associated with variants in the AMHR2 gene. Affected males generally have normal male external genitalia but retain structures derived from the Müllerian ducts, such as a uterus. Around half of affected dogs are cryptorchid, with a risk of complications such as Sertoli cell tumours or pyometra. Genetic testing is recommended before breeding, as affected males with descended testes may be fertile and carriers show no clinical signs.
