In other species: dog , puma , horse , pig , Arabian camel , llama , cattle , goat , sheep

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 100100 (trait) , 219050 (trait) , 314300 (trait)

Mendelian trait/disorder: no

Considered a defect: yes

Key variant known: no

Cross-species summary: Failure of one (unilateral) or both (bilateral) testes to descend.

Species-specific description: Cryptorchidism is a type of XY Disorder of Sexual Development (DSD) characterized by the presence of one or two undescended testes in an otherwise phenotypically normal male (isolated cryptorchidism). It is uncommon in this species. Breeding of affected cats is discouraged.

Edited by Vicki N. Meyers-Wallen, VMD, PhD, Dipl. ACT

Clinical features: Affected cats have either one or two undescended testes. Since verification of scrotal testes by palpation is challenging in young kittens, affected cats are often diagnosed when presented for neutering. The undescended testis may be located anywhere from the caudal pole of the kidney to the inguinal canal, or outside of the canal but cranial to the scrotum (Meyers-Wallen, 2011).

Pathology: Unilateral cryptorchid cats may have reduced fertility and bilateral cryptorchid cats are sterile, as spermatogonia are depleted in undescended testes. Cryptorchid testes can occur in association with other types of XY DSD, such as XY sex reversal (Schlafer et al., 2011; OMIA#000791-9685) and Persistent Müllerian Duct Syndrome (Schulman and Levine 1989; OMIA#000791-9685)).

As testes descend, they transit through the abdomen and inguinal canal to the scrotum. Testosterone and INSL3 (insulin like factor 3), both secreted by Leydig cells, induce growth and differentiation of the gubernaculum, which is needed for normal testicular descent. Mutations in INSL3 or its receptor (LGR8/GREAT) cause cryptorchidism in humans, but analogous mutations have not been investigated in cats. Human males with heterozygous INSL3 mutations are unilaterally cryptorchid at birth, but the testis usually descended at puberty (Tomboc et al., 2000, Ferlin et al., 2003). Other candidate genes for human cryptorchidism include the androgen receptor (AR) and estrogen receptor (ER, Pathirana, 2010).

Prevalence: Feline isolated cryptorchidism is uncommon, ranging from only 1.3% to 1.7% of cats presented for neutering. Most affected cats are unilaterally cryptorchid, and Persians may have a higher prevalence than other breeds (Yates et al., 2003; Millis et al., 1992).

Control: Breeding of fertile cryptorchid animals (as well as their parents or siblings) is discouraged. The AVMA states that it is unethical for a veterinarian to surgically correct cryptorchidism without also sterilizing the animal.

Genetic testing: There are no genetic tests available at this time.