PFK Deficiency in English Springer Spaniels

By Urs Giger Dr. med. vet. FVH, DACVIM
Associate Professor of Medicine
Section of Medical Genetics
School of Veterinary Medicine
University of Pennsylvania
3850 Spruce Street
Philadelphia, PA 19104-6010
and
Loren J. Rossiter DVM
Chairman, Heritable Defects Committee
English Springer Spaniel Field Trial Assoc.
1411 Harrington Drive
Racine, WI 53405

Several hereditary disorders have been described in the English springer spaniel breed. Recently, another inherited disorder has been recognized in this breed. The disorder is called PFK deficiency. It is caused by a genetic deficiency of phosphofructokinase (PFK), an enzyme that plays a major role in the metabolism of sugar. Since this enzyme is central in the production of energy to maintain normal cell structure and Function, springers with PFK deficiency have diseased red blood cells and muscle cells.

PFK deficiency typically causes episodes of mild to life-threatening symptoms. Common signs include intermittent dark urine (orange to coffee-colored), pale gums or jaundice, weakness, fever and inappetence.

Sporadic dark urine is a hallmark finding of PFK deficiency and commonly develops following hyperventili¬ation that accompanies hunting/ exercise, excessive excitement and high environmental temperatures (see Figure 1). The increased respiratory rate that occurs with these stressful situations accelerates destruction of PFK-deficient red blood cells in affected dogs. This results in a lowered red blood cell count (anemia) and the dark urine (hemoglobinuria).

Since skeletal muscle cells are also deficient in PFK enzyme, symptoms related to muscle dysfunction may also occur. These symptoms occur most commonly in hunting springers and include resistance to run for long distances, frequent resting during hunting and muscle cramps.

The symptoms of PFK deficiency typically resolve within hours to days. If situations that induce hyperventilation are avoided, affected dogs have a relatively normal life expectancy. Unfortunately, if a dog with PFK deficiency is a hunting dog, it means the end of his or her hunting career.

PFK deficiency occurs in pet, show and field lines of English springer spaniels. Most of the thirty or so dogs diagnosed with the disorder up to this point have been field-bred springers.

The disease is inherited as a recessive trait. Mating of two carrier animals may produce affected, carrier and normal dogs. Carriers who have no clinical signs of PFK deficiency but carry the defective gene can be detected by a special laboratory test, the same test that is now used to detect affected dogs.

The test that is run to diagnose PFK deficiency and determine the genetic status of dogs, with respect to the disorder, is now being run in Dr. Giger's laboratory at the address above. The test uses a small amount of blood and determines if a dog has two mutant PFK genes (is affected), one normal and one mutant PFK gene (is a carrier), or two normal genes (is normal). This test is one of the first molecular screening tests for competition animals allowing us to determine the gene frequency in the breed and efficiently eliminate affected and carrier dogs from breeding. English springer spaniels that have PFK deficiency or that are carriers should not be used for breeding in order to prevent the further spread of this disease.

This evaluation of PFK was requested by Spaniels In The Field of Loren Rossiter, DVM in response to the article published in the December/January 1991-92 issue of "Gun Dog Magazine". Dr. Rossiter, chairman of the Heritable Defects Committee of the English Springer Spaniel "Parent Club" and Dr. Giger, leading research authority joined in preparing this report.