Pyruvate kinase (PK) deficiency is an inherited disease occasionally encountered in Abyssinian and Somali cats, and also reported in the domestic shorthair cat. 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).

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 signs. Anaemia often results in only vague signs such as lethargy and lack of appetite. However, a rapid severe life-threatening anaemia can also develop. Although PK deficiency is hereditary, the anaemia is usually mild and clinical signs may not be obvious, and thus may not be noticed until the cat is quite old.

 

How is PK deficiency inherited?

The disease is inherited as an autosomal recessive trait (see box 1). This means that a cat can be carrying the defective gene (heterozygous) without having any symptoms of the disease at all. Affected cats (homozygous) arise when two carrier cats are mated with each other. Since carrier cats remain healthy, and the anaemia of affected cats may not be detected until they are a few years of age, the potential exists for carrier cats and affected cats to have had significant numbers of offspring before the disease is identified. However, the positive side of this is that it also means 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 per cent of the offspring will be free of the defective 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.

 

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. A genetic test is available at the Josephine Deubler Genetic Disease Testing Laboratory at the University of Pennsylvania in the US, at the University of California, Davis and at Langford Veterinary Diagnostics, University of Bristol. Affected cats as well as carrier cats can be identified with the test.

 

Why worry about PK deficiency?

PK deficiency is inherited and although predominately a problem in the US it is being reported increasingly in cats throughout Australia, New Zealand and Europe, including the UK. Approximately 2500 cats have been tested at Pennsylvania since 1998, and around 15 per cent of those have been found to carry the defective gene (personal communication, Giger U, 2005). A recent UK survey showed 36 per cent of Somali cats to be carriers.

The Somali Cat Club in the UK is very proactive in tackling the problem of pyruvate kinase deficiency. Following the recent UK survey the Governing Council of the Cat Fancy (GCCF) has changed its registration policies so that all breeding Somali cats need to be tested for it.

 

Updated November 2008