Burmese head defect (BHD)
Kittens with two copies of this gene are born with a badly malformed head and cannot survive. With one copy the cat is healthy, sometimes with a slightly shorter muzzle. In the Burmese and related breeds about 1 in 17 cats is a carrier.
How it is found: DNA test of the parents. Two carriers are never mated with each other; FIFe has required the test since July 2026.

