Male pseudohermaphroditism (testicular feminisation syndrome) due to androgen receptor dysfunction. Animals with an XY karyotype and female phenotype, without functional ovaries and infertile. X-linked recessive inheritance. The test is complementary to the clinical examination and karyotyping.

Cuarto de Milla. Frequencies: limited data.

- Female external phenotype with XY karyotype
- Absence of oestrus and of functional ovaries
- Testicular gonads, often intra-abdominal
- Infertility

The dossier records the regulatory variant AR1 NC_009175.3:g.52728703A>G (NM_001163891.1:c.1A>G). No author or year is stated.

- Genotype mares to detect carriers
- Avoid using carriers if the aim is to eliminate the allele
- Advise on the 50% of affected males in the offspring of a carrier
- Confirm the karyotype in animals with an ambiguous phenotype

Differential diagnosis with XY sex reversal (SRY), 63,X/64,XY mosaicism and other androgen insensitivities (AR2–AR6). Complementary: karyotype and gonadal ultrasound.

1. OMIA:000991 Insensibilidad a andrógenos del caballo (variante AR1)