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Burmese Head Defect (Discovered in the Burmese)

Burmese Head Defect causes severe facial defects when two copies of the variant are present, and affected cats require humane euthanasia shortly after birth.

Found in

1 in 2,500 cats

in our testing

Key Signs

Severe craniofacial malformation in homozygous cats, Brachycephaly in heterozygous cats

Age of Onset

At birth

Present at birth


Autosomal Dominant

For autosomal dominant disorders, cats with one or two copies of the disease variant are at risk of developing the condition. Inheriting two copies of the risk variant may make the risk higher or the condition more severe. They may produce kittens affected with the disorder 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 Burmese Head Defect

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 Burmese Head Defect

Cats with Burmese Head Defect, also known as frontonasal dysplasia, are born with severe craniofacial defects making them unviable and requiring euthanasia soon after birth. The defect is characterized by the absence of a visible nose, protrusion of the meninges and brain through the cranium, abnormal development of the maxillary processes, and ocular degeneration. This severe defect is caused by inheriting two copies of the gene mutation. However, inheriting one copy of the mutation causes the cat to have the desired brachycephalic appearance seen in several breeds. Thus, the inheritance pattern is considered codominant.

Kittens exhibiting the severe form of the disorder at birth are typically humanely euthanized due to welfare concerns.

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 genetic mutation follows an autosomal dominant mode of inheritance. Cats with one copy show the breed desired shortened face and muzzle (brachycephaly), while cats with two copies show severe craniofacial malformation. As one copy of the mutation produces cats with brachycephaly, it is advised to only breed carrier cats with one copy of the Burmese Head Defect mutation to clear cats with no copies of the Burmese Head Defect mutation. About half of the kittens will have one copy of the Burmese Head Defect mutation and half will have no copies of the Burmese Head Defect mutation. This will decrease the likelihood of kittens in the litter developing the severe form of the disease. Carrier to carrier matings are not advised as the resulting litter will likely contain kittens with two copies of the Burmese Head Defect mutation and these kittens are likely to develop the severe form of the disease. Suspected carriers should be tested prior to breeding. Please note: It is possible that disease signs similar to the ones caused by the Burmese Head Defect mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene ALX1
Variant Deletion
Chromosome B4
Coordinate Start 110,088,245
Coordinate End 110,088,254

All coordinates reference FelCat9.0

References & Credit

Credit to our scientific colleagues:

Lyons, L. A., Erdman, C. A., Grahn, R. A., Hamilton, M. J., Carter, M. J., Helps, C. R., Alhaddad, H., & Gandolfi, B. (2016). Aristaless-Like Homeobox protein 1 (ALX1) variant associated with craniofacial structure and frontonasal dysplasia in Burmese cats. Developmental Biology, 409(2), 451–458. View the article