Test Detail

The craniofacial defect of the Burmese is a severe congenital malformation of head development. Affected kittens present midline facial defects (clefts, incomplete facial bones, associated brain anomalies) incompatible with life: they are stillborn or die or are euthanised within the first hours. Carriers of one copy are healthy and the allele was historically associated with shorter muzzles, the so-called contemporary appearance of the breed.

The risk is concentrated in contemporary Burmese lines, especially of American origin, and in breeds that have used those lineages. No reliable carrier frequencies have been published: limited data. The DNA test is the only practical way to identify carriers.

- Kittens stillborn or dying shortly after birth\n- Clefts and midline defects of the face and palate\n- Incomplete or abnormal nasal or maxillary bones\n- Associated brain anomalies (midline malformation)\n- Apparent reduction in litter size due to perinatal losses (warning clue in risk lines)

The defect appeared in American Burmese breeding programmes aimed at shortening the muzzle (contemporary type). Breeders observed litters with severely malformed kittens in the facial midline and genealogical studies pointed to common popular breeding animals, which pointed towards recessive genetics. The phenotype was characterised as a craniofacial development defect and a DNA test was later developed to identify carriers. The historical lesson is relevant: a harmful allele can spread if in single dose it provides a desired trait.

- DNA test of Burmese breeding animals with contemporary type in their pedigree before the first mating.\n- Never cross two carriers: on average, 25% of the litter is born affected.\n- A valuable carrier can be crossed with a clear animal and the offspring intended for breeding tested.\n- Record the result in the pedigrees so that buyers and breeders know the status.

Diagnostic confirmation of affected kittens is anatomopathological (necropsy). Differentiate from other congenital midline defects, such as isolated cleft palate or nasofrontal dermoid cysts, also described in Burmese. In affected animals, humane euthanasia is unavoidable. Remember that selection for an extreme muzzle adds risks inherent to brachycephaly, independent of this gene.

1. Lyons LA, Erdman CA, Grahn RA, et al. Aristaless-Like Homeobox protein 1 (ALX1) variant associated with craniofacial structure and frontonasal dysplasia in Burmese cats. Dev Biol 2016;409(2):451-8. PMID: 26610632
2. Lyons LA. DNA mutations of the cat: the good, the bad and the ugly. J Feline Med Surg 2015;17(3):203-19. PMID: 25701860
3. Noden DM, Evans HE. Inherited homeotic midfacial malformations in Burmese cats. J Craniofac Genet Dev Biol Suppl 1986;2:249-66. PMID: 2878018
4. OMIA:002717-9685 (ALX1). https://omia.org/OMIA002717/9685/