Pyruvate kinase (PK) deficiency - information for owners and breeders
What is PK deficiency?
Pyruvate kinase is an enzyme found within red blood cells which enables them to produce energy to survive. If this enzyme is lacking, the lifespan of the red blood cells is significantly reduced, resulting in a reduction in the number of red blood cells in the circulation (anaemia).
How is PK deficiency inherited?
The disease is inherited as an autosomal recessive trait. This means that a cat can be carrying the defective gene without having any symptoms of the disease.
What signs does it cause?
The main consequence of the disease is the development of anaemia. However since the body can quickly manufacture new red blood cells the anaemia is usually only intermittently detectable. Most of the time the anaemia is either only mild, or occurs gradually, enabling the cat to adapt to the anaemia and not show any obvious symptoms. Anaemia often results in only vague signs such as lethargy and inappetance. However, a rapid severe life-threatening anaemia can also develop. Although PK deficiency is congenital, since the anaemia is usually mild and clinical signs may not be obvious, the anaemia may not be noticed until the cat is quite old.
What tests are available and can carrier cats be detected?
Fortunately a reliable test does exist for PK deficiency. It comprises a DNA test that is performed on either a blood sample or cheek swab.
Why worry about PK deficiency?
- PK deficiency is inherited and although predominantly a problem in the US it is being reported increasingly in cats throughout Australia, New Zealand and Europe, including the UK.
- As described above, the clinical signs that develop can be serious and life threatening.
- Becuase initial clinical signs can be mild or go unnoticed, affected cats may not be identified until after they have had large numbers of offspring.
- Carrier cats do not show any clinical signs at all. The disease occurs when 2 carrier cats are mated with each other. This is important because a large number of carrier cats can arise in a population before PK deficiency is even noticed.
- With any genetic disease, by the time the disease becomes an obvious problem within a population it is much more difficult to control and involves a lot more expense and heartbreak.
The Good News!
- Although we know that the disease is already present in the UK, affected cats do not yet appear to be very prevalent in the UK. Identifying carrier cats can stop PK deficiency becoming a prevalent disease in the UK.
- We can reliably teast for affected cats, including identifying asymptomatic carriers. If carrier cats are identified they can still be used for breeding as long as we ensure that they are NOT mated with another carrier. Mating a carrier with a non-carrier will not produce any offspring that will suffer from PK deficiency and 50% of the offspring will be free of the defectice gene. As long as the offspring are also tested, even carriers can be bred from again as long as it is ensured that they are only mated with a non-carrier cat. In this way, controlled breeding programmes can be implemented so that important lines can be retained within the gene pool.