Genetic test of the variant that determines the hairlessness characteristic of the Sphynx cat. The mutation affects the KRT71 gene, which encodes a hair follicle keratin, and alters normal hair development, leaving an almost bare coat with fine down in some areas. It is not a disease: it defines a breed phenotype with specific dermal care. The test makes it possible to plan crosses and anticipate whether the offspring will have hair or not.

The variant is essentially fixed in the purebred Sphynx population, where the hairless phenotype is the standard. Heterozygotes appear in outcross programs (Devon Rex and domestic shorthair in some registries). As it is a desired and selected trait, it is not appropriate to speak of disease incidence.

- Does not produce signs of disease: it is a phenotype variant\n- Almost complete absence of guard hair, with fine down on the muzzle, ears, paws and tail\n- Skin with folds, increased sebaceous secretion and accumulation of dermal fat\n- Greater loss of body heat and higher metabolism than in a coated cat\n- Sensitivity to sun (burns) and cold\n- Greater tendency to abundant earwax

The breed was born in 1966 in Toronto (Canada), from a hairless kitten born spontaneously in a domestic shorthair litter. The phenotype was consolidated through selective breeding and crosses with the Devon Rex, a breed with which it shares the locus. In 2010, Gandolfi and colleagues identified the molecular basis: the KRT71 c.816+1G>A variant, responsible for the Sphynx hairlessness (hr allele), and demonstrated that the wavy coat of the Devon Rex is due to another allele (re) of the same gene. The hairless Sphynx is also a natural model for studying hair follicle biology.

- Two homozygous Sphynx produce hairless offspring consistently\n- If you cross a Sphynx with a normal-haired non-carrier cat, the entire first generation will have hair and will be carriers\n- Crossing Sphynx with Devon Rex can produce hairless cats (compound heterozygotes) due to allelism at KRT71: know your registry's rules on these outcrosses\n- Use the test to confirm the status before planning outcrosses or importing new lines\n- Do not prioritize the hairless phenotype over cardiac health: maintain HCM screening in the breed

Do not confuse the KRT71 phenotype with other feline hypotrichoses of a different cause or with acquired alopecias (demodicosis, dermatophytosis, psychogenic alopecia). Sphynx skin requires regular hygiene to prevent sebaceous dermatitis and secondary infections, sun protection and environmental thermal control. From a welfare perspective, inform owners of the maintenance the breed requires before acquisition.

1. Gandolfi B, Outerbridge CA, Beresford LG, Myers JA, Pimentel M, Alhaddad H, Grahn JC, Grahn RA, Lyons LA. The naked truth: Sphynx and Devon Rex cat breed mutations in KRT71. Mamm Genome 21(9-10):509-515, 2010. PMID: 20953787
2. Lyons LA. DNA mutations of the cat: the good, the bad and the ugly. J Feline Med Surg 17(3):203-219, 2015. PMID: 25701860
3. OMIA:001583-9685. Hypotrichosis, with whiskers short and curled in Felis catus. https://omia.org/OMIA001583/9685/
4. OMIA:001581-9685. Curly coat, Devon rex in Felis catus. https://omia.org/OMIA001581/9685/