Disorders of sex development (DSD) have long been documented in domestic animal species
including horses. However, there is only a single report of an androgen receptor mutation
causative of such a DSD syndrome in a horse pedigree. Here, we present a new familial AR
mutation in horses. A missense mutation (c.2042G>C) at AR exon 4 explains the segregation of
the DSD in a Thoroughbred horse pedigree. The mutation, expected to affect the ligand-binding
domain of the androgen receptor protein, led to complete androgen insensitivity of XY SRY+,
testicular DSD individuals. Additionally, design of a PCR-RFLP technique provided an accurate
molecular test for identification of horses carrying the mutation.