Pyruvate kinase deficiency

Pyruvate kinase deficiency (PKDef) is an inherited disease that was first documented in Basenjis in the early 1970s but has since been reported in a number of other breeds.

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Pyruvate kinase (PK) is an enzyme found in red blood cells. If this enzyme is lacking, the lifespan of the red blood cells is reduced and this results in anemia (a reduction in the number of red blood cells in the circulation).

The main sign of PK deficiency is anemia. The anemia means that an affected dog appears pale (in their mouth and eyes) and may show signs of weakness and exercise intolerance. The signs may come and go initially which may cause problems with diagnosis.

The clinical signs of anemia are quite variable. Some animals will appear tired and weak, others will lose their appetite, and lose weight. Often the spleen and liver of affected dogs is enlarged but it is unlikely that these signs would be noticed without a veterinary examination. Many dogs eventually die from liver failure.

The disease is usually recognized in dogs between 4 months and one year but some dogs may be several years old before a diagnosis is made. PKDef inevitably shortens a dog’s lifespan and most affected dogs live to be around 4 or 5 – the maximum recorded age for a dog suffering the disease is 8 years.

If anemia is detected then your veterinarian will also want to do some other tests to rule out more common causes such as immune-mediated anemias. Other signs relating to anemia may be present such as increased heart rate and an enlarged liver and spleen. PKDef also causes changes in bone density that may be recognized on X-ray increasing your veterinarian’s suspicion that the disease is present.

In some breeds of dog (Basenji, Beagle, Dachshund, Eskimo, West Highland White, Pug, Cairn Terrier and Labrador Retriever) there is a DNA test for PKDef. This can be performed on a blood sample, or on a sample of cells collected from a cheek swab. If this test is not available it is possible, although more difficult, to test for the enzyme deficiency in the red blood cells.

PKDef is a genetic abnormality that has been recognized in a number of dog breeds. It is caused by a defective gene and affected animals have two copies of this gene. Carrier animals have only one copy of the defective gene and do not show signs of disease. The disease occurs when two carrier animals mate with one other and produce puppies with two defective genes (on average one-quarter of the offspring of two carriers will be affected). Carrier animals can live normal lives and may produce many litters before they are identified as carriers of the disease.

As it is caused by a genetic mutation, there is currently no treatment or cure for the underlying condition. However, the episodes of anemia may be managed. In humans gene therapy is being developed.

PK deficiency can only be prevented by identifying carrier animals and preventing them from reproducing.

For further information, visit the following websites:

• Laboratory for Clinical Diagnostics (LABOKLIN) – PK Deficiency (Pyruvate Kinase Deficiency). Website: www.laboklin.co.uk/laboklin/showGeneticTest.jsp?testID=8015.
• UC Davis Veterinary Medicine, Veterinary Genetics Laboratory – Pyruvate Kinase Deficiency (PKDef). Website: https://www.vgl.ucdavis.edu/services/PKDefDog.php.