What is phosphofructokinase (PFK) deficiency?

The enzyme PFK is important in energy metabolism in red blood cells and in skeletal muscle during intense exercise. PFK deficiency is an inherited disorder that causes premature breakdown (hemolysis) of red blood cells,  and a reduced tolerance for exercise. Affected dogs have chronic mild anemia with intermittent bouts of acute hemolysis, often associated with intense exercise, overheating or prolonged barking.

How is PFK deficiency inherited?

This is an autosomal recessive trait which means both parents of an affected dog are carriers of the disorder. Carriers have about one half normal enzyme activity in red blood cells and muscle tissue, and are clinically unaffected.

What breeds are affected by PFK deficiency?

The disorder occurs most commonly in English springer spaniels and is also seen in American cocker spaniels.

For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have only listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.

What does PFK deficiency mean to your dog & you?

Affected dogs have a persistent mild anemia (low levels of red blood cells) for which they are generally able to compensate. Intermittently they will have acute episodes of red blood cell breakdown (hemolysis), when they become lethargic and weak. This is usually associated with intense exercise or excessive barking or panting.   Their mucous membranes (eg. gums) are pale or jaundiced and they usually run a high fever. You may notice the urine is brown due to the excretion of blood breakdown products. At these times your dog will require veterinary attention.

Dogs with this condition can have a normal life span. Management of this condition requires avoidance of stress, strenuous exercise, overheating and over excitement.

How is PFK deficiency diagnosed?

Based on clinical examination and blood tests, your veterinarian will diagnose hemolytic anemia (low levels of red blood cells due to increased breakdown) in your dog. Further tests will be required to diagnose this specific condition.

For the veterinarian:

CLINICAL: persistent compensated hemolytic anemia (PCV at or near normal) with intermittent hyperventilation-induced hemolytic crises with (usually mild) exertional myopathy, poor exercise tolerance; during hemolytic crisis, see lethargy, weakness, hepatosplenomegaly, muscle wasting, pale or icteric mucous membranes, pyrexia (to 41 degrees Celsius).

LABORATORY: A specific genetic test can identify carriers and affected animals at any age (see reference below). Affected and carrier dogs can also be identified based on PFK activity in blood samples. Check with your clinical pathology lab for requirements for sample submission.

How is PFK deficiency treated?

There is no specific treatment for this disorder, other than removal of affected and carrier dogs from the breeding population.

The condition can be well-managed, and your veterinarian will discuss this with you. You will need to be alert for signs associated with increased intravascular hemolysis (red cell breakdown), such as weakness, lethargy, pale or jaundiced mucous membranes, or brownish urine. It is also important to avoid stressful situations, strenuous exercise, excitement that will cause a great deal of barking, and high environmental temperatures.

Your veterinarian will give supportive care as needed during an episode of severe hemolysis.

For the veterinarian: Aspirin or dipyrone can be used to treat the fever which accompanies IV hemolysis, and may  potentiate the hemolytic anemia. IV fluids are recommended with severe IV hemolysis; blood transfusions are usually not required.

Breeding advice

Because this is an autosomal recessive trait, both parents of affected dogs carry the defective gene. Neither affected (homozygous) or carrier dogs (heterozygous) should be used for breeding. There is a DNA test that can identify carrier dogs at any age (see reference below). Many affected and carrier dogs have already been removed from the breeding population.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources

Harvey, J.W. 1995. Congenital hemolytic anemias and methemoglobinemias.  ACVIM-Proceedings of the 13th Annual Veterinary Medical Forum: 37-40.

http://www.vetgen.com  - information on genetic testing available

Copyright 1998 Canine Inherited Disorders Database. All rights reserved.
Revised: October 30, 2001.

This database is funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association.