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Hypotrichosis (Discovered in the Birman)

Hypotrichosis is a disorder of the immune system causing kittens to be born hairless and to develop serious infections.

Key Signs

Hairlessness, Immunodeficiency

Age of Onset

At birth

Present at birth


Autosomal Recessive

For autosomal recessive disorders, cats with two copies of the variant are at risk of developing the condition. Cats with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their kittens if bred.

Likelihood of the Condition

High likelihood

At risk cats are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a cat with Hypotrichosis

Partner with your veterinarian to make a plan regarding your cat’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about Hypotrichosis

Hypotrichosis is caused by a point mutation in the FOXN1 gene, which leads to aplasia of the thymus and abnormal development of lymphoid tissue in multiple organs, including the spleen, Peyer's patches, and lymph nodes. Kittens affected by the disease are born hairless and have an increased susceptibility to infections. Some kittens die soon after birth. Kittens which survive the postnatal period develop fragile, shortened, sparse fur with wrinkled, greasy-looking skin. Most affected kittens die or are euthanized before eight months of age because of serious infections occurring in locations such as the respiratory or digestive tracts.

Upon initial observation of clinical signs, affected kittens should be closely monitored to assess welfare and devise a supportive care treatment plan. Due to the susceptibility to and severity of secondary infections, affected cats are often euthanized for welfare reasons before one year of age.

For Breeders

Planning to breed a cat with this genetic variant?

There are many responsibilities to consider when breeding cats. Regardless of test results it is important that your cat is in good general health and that you are in a position to care for the kittens if new responsible owners are not found. For first time or novice breeders, advice can be found at most cat registry websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier cat with one copy of the Hypotrichosis mutation can be safely bred with a clear cat with no copies of the Hypotrichosis mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the Hypotrichosis mutation. Kittens in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected kittens. Please note: It is possible that disease signs similar to the ones caused by the Hypotrichosis mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene FOXN1
Variant Deletion
Chromosome E1
Coordinate Start 18,255,880
Coordinate End 18,255,883

All coordinates reference FelCat9.0

References & Credit

Credit to our scientific colleagues:

Abitbol, M., Bossé, P., Thomas, A., & Tiret, L. (2015). A Deletion in FOXN1 is associated with a syndrome characterized by congenital hypotrichosis and short life expectancy in Birman cats. PLoS ONE, 10(3). View the article