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.

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.