A genetic mutation in Burmese cats affects the development of the head and facial areas of the foetus during pregnancy.

The craniofacial malformations caused by the condition are immediately apparent from birth and are severe, eg malformation of the lower jaw and nostrils, degeneration of the eyes and ears and protrusion of the brain.

Affected kittens can be born alive and require euthanasia as the condition is incompatible with normal or prolonged life.