Information about PK Def for Bengal and Singapura breeders
Pyruvate kinase deficiency (PK Def) has traditionally been thought of as an inherited genetic disease of Abyssinian and Somali cats. Recently, however, PK Def has been identified in Bengal and Singapura cats too.
What is PK Def?
Pyruvate kinase is an enzyme important for red blood cell energy metabolism. Therefore, if this enzyme is lacking, a haemolytic anaemia can result due to red blood cells being prematurely destroyed in the circulation. In PK Def, there is a genetic mutation that means that this enzyme is not produced.
My cat has been diagnosed with PK Def, should I worry?
The resulting anaemia is often mild and intermittently detectable, or may not become evident until the cat is older, so there is not usually cause for immediate concern. Indeed some cats never show clinical signs associated with PK Def. Signs to look out for are lethargy and inappetence. A rapid severe life-threatening anaemia can also develop but this appears to be relatively rare from the cases we are aware of; in these cases it is possible that stressful situations may predispose to the development of clinical signs.
How is PK Def inherited?
The disease is inherited as an autosomal recessive trait, so only cats homozygous (with two copies) for the defective gene are affected. Clinical signs due to PK Def will only occur in homozygous affected cats, but, as described above, they are variable and some cats will not show signs of PK Def at all. Heterozygous carrier cats (with only one copy of the defective gene) are clinically healthy and are not affected by the disease, but they can pass the defective gene to their offspring.
How is PK Def diagnosed?
A PCR test can be performed to identify the genetic mutation. This can be performed on a buccal swab or a blood sample. Please note, we can test Bengals for PK Def but we cannot test the Asian Leopard Cat due to sequence differences between domestic and wild cats
What do the different test results mean?
A Normal PK Def genetic test result means that the cat does not have the genetic mutation causing PK Def.
A Heterozygous (carrier) PK Def genetic test result means that the cat has one copy of the mutation. The cat will not have PK Def, but may pass the mutation to their offspring.
A Homozygous (affected) PK Def genetic test result means that the cat has two copies of the mutation. The cat will have PK Def.
Should we immediately neuter all cats that have the defective gene?
No! It is important to remember that genetic diseases are more likely to arise when the gene pool within a breed is small. This is typically the case in breeds with low numbers of cats that are related and often bred together. If a significant proportion of cats carry the defective gene for PK Def, neutering would only reduce the number available for breeding and, therefore, reduce the gene pool even further. This increases the chances of other genetic diseases arising.
Should we breed from affected cats?
Whilst it is preferable not to breed from affected cats in the medium to longer term, in order to preserve the 'good genes' from affected cats it is permissible to breed affected cats with normal cats (no copies of the defective gene). This does not risk producing any affected kittens, but will produce carrier cats. These carrier cats can then be bred to other normal cats, thereby producing more cats that are normal and do not carry the defective gene. If this method is used to preserve breeding lines, it is preferable to use affected male cats where possible as affected females could become ill during pregnancy with risk of anaemia developing.
Should we stop breeding?
There is no need to stop breeding, but it is important to ensure that you test for PK Def before breeding, and careful breeding programmes will be needed in order to gradually eliminate the disorder from the breed.
How do we breed safely to avoid producing affected kittens, whilst still maintaining a good gene pool?
Cats have two copies of the PK gene, so can be Normal (-/-), Carrier (+/-) or Affected (+/+) depending on how many copies of the defective PK gene (+) they have. Below are shown various matings between Normal, Carrier and Affected cats.
Matings to avoid
Matings that can be safely carried out
(*It is preferable if the affected cat is a male since a female could become ill during pregnancy)
Strategic and controlled breeding of affected and carrier cats to normal cats is important for preserving the gene pool and retaining important lines.
More Information
- Information for Bengal breeders on the number of cats tested for PK Def can be found here
- Information for Singapura breeders on the number of cats tested for PK Def can be found here
- Information on how to take and submit mouth swabs for genetic testing can be found here
- Information about pyruvate kinase deficiency at the Feline Advisory Bureau website