Hypotrichosis in the Birman cat

Hypotrichosis is a congenital hair growth disorder. Birman kittens are born hairless, and later develop sparse, shortened and downy fur with wrinkled, grease-looking skin. This defect is associated with underdevelopment of the thymus and loss of lymphocytes in the spleen and lymph nodes. The consequence is respiratory, digestive or skin infections leading to shortened life expectancy.

The disease is caused by mutation c.1030_1033del in the FOXN1 gene.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected kittens.

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References:

Abitbol, M., Bossé, P., Thomas, A., Tiret, L. : A deletion in FOXN1 is associated with a syndrome characterized by congenital hypotrichosis and short life expectancy in Birman cats. PLoS One 10:e0120668, 2015. Pubmed reference: 25781316