Pyruvate Kinase Deficiency

TL;DR. Pyruvate kinase deficiency is an uncommon, inherited genetic disorder in dogs and cats that causes red blood cells to break down prematurely, leading to chronic anemia, progressive bone marrow scarring, and potential liver failure.

Pyruvate kinase deficiency is an inherited condition that can affect both dogs and cats.

What is it?

Pyruvate kinase deficiency is an inherited disease that affects the red blood cells (erythrocytes) of dogs and cats. To understand this condition, it helps to look at how red blood cells function. These cells are the body's oxygen delivery trucks. They travel through the bloodstream, picking up oxygen from the lungs and delivering it to tissues and organs throughout the body. Because red blood cells do not have a nucleus or mitochondria when they are mature, they rely entirely on a chemical process called glycolysis to generate energy.

The key engine of this energy production is an enzyme called pyruvate kinase. This enzyme helps produce adenosine triphosphate (ATP), the primary energy currency of the cell. Without enough pyruvate kinase, red blood cells cannot produce the energy they need to maintain their cell membranes and keep their shape. As a result, these fragile cells swell, deform, and rupture prematurely in a process called hemolysis. This constant destruction of red blood cells leads to hemolytic anemia.

Initially, the animal's body attempts to compensate for this loss. The bone marrow works overtime, flooding the bloodstream with immature red blood cells (reticulocytes) in an attempt to keep up with the demand. This is known as an extremely regenerative anemia. However, this intense compensation cannot last forever. Over time, the constant cellular destruction and the accumulation of iron from the broken-down cells cause severe damage. The bone marrow eventually develops scarring (myelofibrosis) and hardens (osteosclerosis). Once the bone marrow is scarred, it can no longer produce new blood cells, and the anemia progresses to a nonregenerative, life-threatening state. Additionally, the excess iron released from the ruptured cells can accumulate in the liver, leading to liver damage and potential liver failure.

Causes & risk factors

Pyruvate kinase deficiency is a purely hereditary condition. It is caused by a genetic mutation that is passed down from parents to their offspring. The disease is inherited in an autosomal recessive pattern. This means that an affected animal must inherit two copies of the mutated gene—one from the mother and one from the father—to actually develop the disease.

Animals that inherit only one copy of the mutated gene are known as carriers (or heterozygotes). These carriers do not show any clinical signs of the disease and live normal, healthy lives. However, they can pass the mutated gene on to their offspring. If two carriers are bred together, there is a 25 percent chance that each puppy or kitten in the litter will inherit two copies of the gene and be affected by pyruvate kinase deficiency.

While heritable hemolytic anemia is uncommon in the general pet population, it can be highly prevalent within specific breeds or family lines where the mutated gene has been passed down through generations. As noted in a leading veterinary internal medicine reference:

"Although heritable HA is relatively uncommon, heritable defects may be common in a given breed... When present, hemolysis is more likely to be detected in young adults than in puppies or kittens."
— Small Animal Critical Care Medicine, p. 653

This means that even though the disease is present from birth, the signs of red blood cell destruction often do not become obvious until the pet reaches young adulthood.

Signs to watch for

The symptoms of pyruvate kinase deficiency are primarily related to the lack of oxygen delivery to the tissues (anemia) and the body's efforts to process the debris from ruptured red blood cells. Because the disease progresses gradually, many pets adapt to their low red blood cell counts over time, and their symptoms may seem mild at first.

• Anemia (Cardinal): A severe shortage of healthy red blood cells, which is the defining feature of this disease.
• Lethargy (Common): A general lack of energy; the pet may sleep more than usual or seem unusually sluggish.
• Pallor (Common): Pale or white gums and tongue, instead of a healthy, vibrant pink.
• Exercise intolerance (Common): Tiring very quickly during normal play, walks, or physical activity.
• Decreased overall activity (Common): A general reluctance to run, jump, climb stairs, or engage in daily routines.
• Myelofibrosis (Common): Scarring of the bone marrow tissue, which occurs as the disease progresses and prevents the production of new blood cells.
• Osteosclerosis (Common): Hardening and thickening of the bone cavities where bone marrow resides, visible on diagnostic imaging.
• Icterus (Occasional): Also known as jaundice, this is a yellowing of the gums, the whites of the eyes, or the skin, caused by a buildup of bilirubin (a yellow pigment produced when red blood cells break down).
• Hemosiderosis-associated hepatic failure (Occasional): Liver failure resulting from toxic levels of iron accumulating in the liver tissue over time.

Pale gums (pallor) are a key clinical sign of anemia in affected pets.

How vets diagnose it

Diagnosing pyruvate kinase deficiency requires a systematic approach, starting with routine blood work and moving toward highly specialized genetic tests.

Your veterinarian will first perform a complete blood count (CBC) to assess your pet's red blood cell levels. The CBC measures several parameters, including the hematocrit (HCT), hemoglobin (Hb) concentration, and the total red blood cell count. As explained in a prominent veterinary internal medicine textbook:

"From a practical standpoint, when evaluating the erythroid series, the clinician does not need to assess all the values in the complete blood count (CBC) because several of them provide identical information. For example, the HCT, Hb concentration, and RBC count provide the same type of information—an increase in the number of RBCs usually results in an increased HCT and Hb concentration, and vice"
— Internal Medicine, p. 1235

In the early stages of pyruvate kinase deficiency, the CBC will reveal a severe anemia, but it will also show a massive increase in reticulocytes (immature red blood cells). This tells the vet that the bone marrow is actively trying to replace the destroyed cells. As the disease progresses and bone marrow scarring (myelofibrosis) sets in, the reticulocyte count will drop, signaling that the anemia has become nonregenerative.

To confirm that the anemia is caused by pyruvate kinase deficiency specifically, your vet will need to utilize specialized testing. Physical and functional tests of the red blood cells can measure the actual activity level of the pyruvate kinase enzyme within the cells. However, these functional tests are highly specialized and not available at standard commercial laboratories. As noted in veterinary literature:

"Physical and functional tests are available from only a few laboratories (e. g. , Josephine Deubler Genetic Disease Testing Laboratory for Companion Animals at the School of Veterinary Medicine, University of Pennsylvania)."
— Small Animal Critical Care Medicine, p. 653

The Gold Standard: Genetic Testing
Today, DNA-based genetic testing is the gold standard for diagnosing pyruvate kinase deficiency. These tests are highly accurate, non-invasive (often requiring only a simple cheek swab or a small blood sample), and widely available through veterinary genetics laboratories. Genetic testing identifies the specific breed-related mutations responsible for the enzyme deficiency. Crucially, genetic tests can identify healthy carriers (heterozygotes) who carry one copy of the mutated gene but show no symptoms, allowing breeders to make informed decisions and prevent the disease from being passed on to future generations.

Genetic testing is the gold standard for identifying pyruvate kinase deficiency and carrier animals.

Treatment options

Currently, there are no specific drug treatments, medications, or gene therapies available to cure pyruvate kinase deficiency in dogs or cats. Because the underlying cause is a genetic blueprint error, treatment is primarily supportive and focused on managing symptoms, maintaining quality of life, and addressing complications as they arise.

• Blood Transfusions: During periods of acute hemolytic crisis, when red blood cell counts drop to dangerously low levels, life-saving blood transfusions may be necessary to stabilize your pet. However, transfusions only provide temporary relief, as the transfused cells will eventually be broken down by the body as well.
• Managing Iron Overload: Because the constant destruction of red blood cells releases large amounts of iron into the body, vets may monitor liver enzymes and iron levels closely. In some cases, iron-chelating therapies (medications that bind to excess iron so it can be excreted) may be discussed, though their use in pets with this condition is highly specialized and must be managed carefully.
• Splenectomy: In some affected dogs, surgical removal of the spleen (splenectomy) may be considered. The spleen is the primary organ responsible for filtering out and destroying damaged red blood cells. Removing the spleen can sometimes extend the lifespan of the red blood cells, reducing the severity of the anemia. However, this procedure does not stop the progression of bone marrow scarring (myelofibrosis) and carries surgical risks, so it is evaluated on a strict case-by-case basis.
• Bone Marrow Transplantation: While bone marrow transplantation could theoretically cure the disease by replacing the defective stem cells with healthy ones, this procedure is extremely rare, highly complex, cost-prohibitive, and carries significant risks of life-threatening complications. It is not widely available in veterinary medicine.

Prognosis

The long-term prognosis for pets with pyruvate kinase deficiency varies significantly between species, and because this is an uncommon condition, comprehensive long-term survival data is limited.

In dogs, the prognosis is generally guarded to poor. Most affected dogs experience a rapid progression of bone marrow scarring (myelofibrosis) and hardening (osteosclerosis). This progressive damage typically leads to severe, nonregenerative anemia or liver failure by the time the dog is 3 to 5 years old. Despite supportive care, many dogs succumb to the disease or are humanely euthanized due to a declining quality of life in early adulthood.

In cats, the disease course is often much more variable and sometimes more favorable. Many affected cats can tolerate chronic, moderate anemia surprisingly well and may live for several years, sometimes reaching late adulthood. However, they remain at constant risk for sudden hemolytic crises, progressive liver damage, and eventual liver failure. Regular veterinary monitoring is essential to track their red blood cell levels and liver health.

Prevention

Because pyruvate kinase deficiency is an inherited genetic disorder, it cannot be prevented through lifestyle changes, dietary modifications, or vaccinations. The only way to prevent this disease is through responsible breeding practices.

If you own a breed that is predisposed to pyruvate kinase deficiency, genetic screening is highly recommended before breeding. DNA tests can easily identify healthy carriers who carry one copy of the mutated gene. Breeders should never mate two carriers together, as this carries a high risk of producing affected puppies or kittens. By utilizing genetic testing, breeders can systematically eliminate the mutated gene from their breeding lines, preventing future generations from suffering from this debilitating condition.

When to call your vet

If your pet has been diagnosed with pyruvate kinase deficiency, or if you suspect they may be showing signs of anemia, close monitoring is vital. You should contact your veterinarian immediately if you notice any changes in their energy levels, gum color, or behavior.

Seek emergency veterinary care immediately if your pet exhibits any of the following red flag signs:

• Extreme weakness or sudden collapse
• Rapid, labored, or open-mouthed breathing
• Yellowing of the gums, skin, or the whites of the eyes (icterus)
• Dark, orange, or tea-colored urine
• Complete refusal to eat or drink

These signs indicate a severe hemolytic crisis or advanced liver dysfunction that requires immediate medical stabilization.

For specific breeds

Pyruvate kinase deficiency is known to affect specific breeds of dogs and cats due to inherited genetic mutations within those gene pools. If you own or plan to adopt one of the following breeds, ask your breeder for documentation of genetic clearance for pyruvate kinase deficiency.

Predisposed Cat Breeds:

• Abyssinian
• Bengal Cat
• American Shorthair
• Singapura
• Egyptian Mau
• LaPerm
• Maine Coon
• Norwegian Forest Cat
• Savannah Cat
• Siberian Cat
• Somali

Predisposed Dog Breeds:

• American Eskimo Dog
• Basenji
• Beagle
• Cairn Terrier
• Pug
• Chihuahua
• Dachshund
• Labrador Retriever
• Poodle (including Miniature Poodle)
• West Highland White Terrier

Sources

• Small Animal Critical Care Medicine, 2nd Edition, p. 653
• Internal Medicine, 5th Edition, p. 1235