PKD - Polycystic kidney disease

Polycystic kidney disease is an inherited disorder commonly present not only in cats, but also in other animals and humans. Persian and exotic Persian-outcrossed breeds are in the highest risk of feline PKD due to frequent inbreeding.

The disorder presents itself as the formation of fluid-filled renal cysts. The cysts disrupt the function of kidneys and can lead to the ultimate renal failure and death of affected animal.  The course of disease depends on magnitude and number of renal cysts. Microscopic cysts are present at birth, but with time they gradually enlarge and in adult animal they can reach several centimetres in diameter. In most animals, the cysts grow slowly, and the signs of disease don´t develop before seven or eight years of age. On the other hand, in some cats, the disease progresses much faster and there is no way to foretell the course of disease in individual animals.

In PKD affected cats, the disease was linked to the feline PKD1 gene, coding polycystin, a protein similar to the transmembrane receptor. PKD is caused by c.10063C>A station in exone 29 PKD1 gene resulting in a premature stop codon. This mutation was found among Persians, Siamese and several exotic, Persian-outcrossed breeds. (Lyons A. L. et al. 2004).

Feline PKD is inherited as an autosomal dominant trait. That means the disease affects all cats bearing mutated PKD1 gene (there are no healthy carriers of the disease). One positive parent is enough to transmit the mutation.  When mating the affected heterozygote (N/P) with the healthy individual (N/N), the mutation is transmitted in 50 % of cases - there is a 50 % risk of transmitting the disease.

In case of mating of two affected animals (N/P x N/P), 50 % of the offspring will suffer from (N/P) and 25 % of the offspring will be healthy (N/N). The 25 % of dominant homozygotes (P/P) with high probability die before birth, skewing the observed ratio in living kittens in such litters to 66 % of heterozygotes and 33 % of healthy individuals.

All cats that carry the abnormal gene are affected with PKD. It is important to identify affected cats before they reach breeding age. Animals with no severe health problems and often normal life-span can be PKD positive. Therefore, we recommend to test all at-risk animals, so that it can be prevented to breed from them.

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PKD affected breeds

High risk: Persian and Exotics, Asian, incl. Burmil and Tiffany, Birma, Scottish Fold, British Shorthair, Cornish Rex, Devon Rex, Ragdoll, Snowshoe

Mid risk: Angora, Maine Coons, Norwegian Forest, Oriental, Siamese, Tonkinese, Turkish Van

Low risk: Abyssinian, Balinese, Bengalese, Burma, Egyptian Mau, Korat, Ocicat, Russian Blue, Singapore, Somali

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References:
Leslie A. Lyons, David S. Biller, Carolyn A. Erdman, Monika J. Lipinsky, Amy E. Young, Bruce A. Roe, Baifang Qin, Robert A. Grahn: Feline Polycystic Kidney Disease Mutation Identified in PKD1, J Am Soc Nephrol 15: 2548-2555, 2004

Semerád M. PKD (Polycystic Kidney Disease) ledvinové onemocnění díl I., [online], [1 June 2008], http://www.allcats.cz/view.php?cisloclanku=2004091102

Semerád M. PKD (Polycystic Kidney Disease) ledvinové onemocnění díl II., [online], [1 June 2008], http://www.allcats.cz/view.php?cisloclanku=2004091103