Pyruvate Kinase Deficiency

Pyruvate Kinase Deficiency

Pyruvate Kinase Deficiency, or PK Deficiency, is the lack of a critical red blood cell enzyme (pyruvate kinase), which regulates the final step in the conversion of glucose to energy. As a result, red blood cells are not able to metabolize the energy required for the cells to function normally, which leads to a change in the cell membranes, a buildup of sodium ions inside the cell, a resulting swelling of the cell (as water molecules follow the buildup of sodium), and an eventual lysing (bursting) of the cell. Furthermore, there is a shortened life span of red blood cells as the abnormal cells are destroyed by the spleen and liver. To make matters worse, PK deficiency, through the changes described above, can shift the normal process by which hemoglobin stores and releases oxygen to body tissues. The end result of these changes produces "hemolytic anemia," which is a reduction in red blood cells and tissue oxygenation due to the rupture of abnormal red blood cells.

PK Deficiency Inheritance
Pyruvate Kinase Deficiency is an autosomal recessive trait, which means that, for a dog to have PK Deficiency, both parents must be either affected dogs themselves or carriers. Affected dogs will have two copies of the bad gene, while carriers will only have one copy and will not clinically show symptoms, although studies have shown that carriers do have a reduction in normal red blood cell enzyme activity.

Breeds Affected
Pyruvate Kinase Deficiency affects Basenjis most commonly, but has also been seen in Beagles and West Highland White Terriers.

Diagnosis and Treatment
PK Deficiency can be diagnosed by a blood test which measures PK levels in the red blood cells. However, a genetic test has been introduced for the Basenji and the West Highland White Terrier which identifies the causative gene, and can therefore identify both affected dogs and carriers.

There is no treatment for PK Deficiency. Affected dogs are typically diagnosed before 1 year of age, due to visible symptoms like fatigue, reduced tolerance of exercise, pale gums, and other signs of anemia. They typically die from the disease before 4 years of age, due to liver failure or bone marrow failure.

Breeding Decisions
Clearly, affected dogs should be spayed/neutered. Because of the severity of this condition, most experts recommend not breeding carriers either. A concerted effort by the Basenji community has significantly reduced the prevalence of the PK Deficiency gene. Responsible breeding can completely eliminate the gene from the population.