What Is Pyruvate Kinase Deficiency?

A Review of Pyruvate Kinase: A Rare Cause of Anemia

Newborn under bili lights
Newborn under bili lights. AndyL/Creative RF/Getty Images

Learning you or your loved one has PK deficiency can be frightening. You may wonder, how did I get this? Or what are the treatment options? Hopefully, this basic review of the condition will answer some of these questions.

Pyruvate kinase (PK) deficiency is a rare inherited form of anemia. Pyruvate kinase is an enzyme, or chemical, found within the red blood cell required to make energy. Without this crucial enzyme, the red blood cell breaks down more rapidly.

This red blood cell breakdown is called hemolysis and PK deficiency is classified as a hemolytic anemia.

People with PK deficiency are born with this condition. It is inherited an autosomal recessive pattern meaning that both parents have to be carriers for the disorder. If each parent is a carrier for PK deficiency, they have a 1 in 4 chance of having a child with PK deficiency.

Symptoms

Symptoms of PK deficiency can begin early in life. It is not uncommon for newborns with PK deficiency to develop jaundice (yellowing of the skin) in the first day of life. This jaundice is usually more severe than physiologic jaundice that newborns typically develop between day 2 and 5 of life. The medical term for jaundice is hyperbilirubinemia.  Bilirubin is a pigment found in red blood cells. The rapid destruction of red blood cells in PK deficiency increases the amount of bilirubin in circulation.

Otherwise, people with PK deficiency have symptoms of anemia: pale skin, fatigue or tiredness, rapid heart rate, or shortness of breath.

Some people with PK deficiency will develop an enlarged spleen, called splenomegaly.

Diagnosis

Similar to other forms of anemia, the complete blood count (CBC) provides the first clue. The anemia associated with PK deficiency can be severe resulting in a very low hemoglobin and/or hematocrit. Like other hemolytic anemias, the reticulocyte count (recently made red blood cells) will be elevated.

PK deficiency can be confirmed by sending blood work to specialty labs to detect the low level of PK within the red blood cells. Alternatively, genetic tests that look for mutations are becoming a more common diagnostic test for this condition.

Complications

As reviewed earlier, the breakdown of red blood cells results in increased levels of bilirubin.  The increased bilirubin can build up sludge in the gallbladder and eventually lead to the development of gallstones.

People with PK deficiency can also develop iron overload. This complication is most common in people who require frequent blood transfusions to treat their severe anemia. However, this can occur in people who do not have a significant transfusion requirement as well. 

Like all people with hemolytic anemias, people with PK deficiency are at risk for transient aplastic crisis. This is caused by a parvovirus B19 infection (which causes Fifth Disease in children). The parvovirus prevents the bone marrow from making new red blood cells for 7 to 10 days.

Without the ability to replace the rapidly destroyed red blood cells, severe anemia can develop and transfusion may be required until production returns to normal.

The severe anemia associated with PK deficiency can occur in children even before they are born. This condition is called hydrops fetalis; this can be severe and result in a pregnancy loss. Sometimes this can be treated with intrauterine (through the uterus) transfusions to the fetus.

Treatment

Some physicians may give you folic acid to take daily. Folic acid is a vitamin needed to make new red blood cells. Many of food in the United States are fortified with folic acid as well.

Typically, severe anemia is treated with blood transfusions. Some people with PK deficiency require transfusions every 3 to 4 weeks. Other people may only require transfusions occasionally during times of illness or stress.

If the levels of bilirubin reach critical levels in newborns, an exchange transfusion may be required. In this procedure blood is removed from the infant (also removing bilirubin) and this blood is replaced with transfused blood.

Gallstones caused by PK deficiency may need to be removed with cholecystectomy, surgical removal of the gallbladder. Splenectomy, surgical removal of the spleen, might be performed in an effort to reduce the severity of the anemia, particularly in people who require frequent transfusion. Unfortunately, splenectomy does not work for everyone with PK deficiency.

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