Siamese — questions to ask before paying a deposit
A responsible breeder will have these readily available. Deflection is a red flag.
Systemic (AA) amyloidosiscan shorten life or cause chronic pain
Amyloidosis is a build-up of abnormal protein deposits, mainly in the liver, that is generally fatal once advanced; it has been studied for decades in Siamese and Oriental lines and tends to appear between one and seven years old. Its inheritance is complex — pedigree analysis points to a mix of one or a few major genes plus smaller background effects — and while researchers have found DNA markers associated with it, there is not yet a commercial diagnostic test.
Ask to see: No commercial DNA screening test currently exists. Ask the breeder about any history of sudden liver or kidney failure, or unexplained early deaths, among related cats.
"Generalized AA-amyloidosis in Siamese and Oriental cats", 1997 (PubMed) (https://pubmed.ncbi.nlm.nih.gov/9220576/) · "Familial amyloidosis in cats: Siamese and Abyssinian AA proteins differ in primary sequence and pattern of deposition", Amyloid, 1999 (PubMed) (https://pubmed.ncbi.nlm.nih.gov/10524286/) · "Single Nucleotide Polymorphisms Associated with AA-Amyloidosis in Siamese and Oriental Shorthair Cats", Genes (MDPI), 2023 (PubMed) (https://pubmed.ncbi.nlm.nih.gov/38136948/) · UFAW — Siamese: Amyloidosis (https://www.ufaw.org.uk/cats/siamese---amyloidosis)
Progressive retinal atrophy (PRA-rdAc / CEP290)can shorten life or cause chronic pain
This inherited retinal disease causes slow, progressive vision loss and eventual blindness. It was first identified in Abyssinians and is often sold as an 'Abyssinian test', but a large-scale genetic survey of over 11,000 cats found the same mutation at high frequency — roughly a third of the Siamese tested — making it a genuine concern for this breed as well.
Ask to see: PRA-rdAc (CEP290) DNA test result for both parents (UC Davis VGL or an equivalent laboratory)
UC Davis VGL — Progressive Retinal Atrophy (PRA rdAc) (https://vgl.ucdavis.edu/test/pra-rdac) · Anderson et al. 2022, "Genetic epidemiology of blood type, disease and trait variants, and genome-wide genetic diversity in over 11,000 domestic cats", PLOS Genetics (https://journals.plos.org/plosgenetics/article?id=10.1371%2Fjournal.pgen.1009804)
Mucopolysaccharidosis VI (MPS VI)can shorten life or cause chronic pain
Mucopolysaccharidosis VI is an inherited enzyme deficiency. Its severe form causes stunted growth, joint disease and hind-limb weakness or paralysis by around eight months old; a milder form can leave a cat looking outwardly healthy. UC Davis's genetics laboratory specifically lists Siamese among the breeds it recommends testing for this condition.
Ask to see: Mucopolysaccharidosis VI (MPS VI) DNA test result for both parents (UC Davis VGL or an equivalent laboratory)
UC Davis VGL — Mucopolysaccharidosis VI (MPS VI) (https://vgl.ucdavis.edu/test/mps-vi-cat)