Pyruvate kinase deficiency is an inherited blood disorder caused by defects in the pyruvate kinase enzyme. The enzyme is essential for healthy red blood cells in the body. Anemia is the primary complication of pyruvate kinase deficiency, and this enzyme deficiency is the second most common cause of hemolytic anemia, according to the University of Maryland Medical Center. Outcomes of the disease vary depending on the severity, but treatments can help alleviate symptoms.
Pyruvate Kinase and Red Blood Cells
Red blood cells travel through the bloodstream delivering oxygen to the tissues of the body while removing waste products. Pyruvate kinase is used by red blood cells to catalyze or speed up chemical reactions that generate energy, in the form of ATP, to build and maintain a strong cell membrane, according to an article by Schroter et al. in the July 1978 issue of "Blut." Pyruvate kinase deficiencies cause red blood cells to break down more easily as the cell's energy requirements for proper cell functioning and membrane stability are not met. Under normal circumstances, red blood cells survive in the body for approximately 120 days before they are broken down, removed and replaced.
Causes
Pyruvate kinase deficiency is caused by a mutation in the PKLR gene, which makes the pyruvate kinase enzyme. Mutations may lead to a complete lack of pyruvate kinase or suboptimal levels of the enzyme. It is a recessive mutation, meaning that a child must receive a bad copy of the PKLR gene from both parents to develop the disease. In general, pyruvate kinase deficiency appears at equal rates across gender and ethnicities, with a slightly higher prevalence in the Amish, according to the University of Maryland Medical Center.
Symptoms
Hemolytic anemia is the primary result of a lack of pyruvate kinase. It is defined as a blood condition in which red blood cells are destroyed before the completion of their normal life span. The lost red blood cells are unable to be replaced by the body fast enough, leading to lower than normal levels in the blood. Generally, the most noticeable symptom of anemia is mild to severe tiredness or fatigue due to a lack of oxygen being delivered to the cells. Other symptoms include jaundice or yellowing of the skin and whites of the eye, enlarged spleen, pale skin color and the development of gallstones, according to the National Heart, Lung and Blood Institute.
Diagnosis
Several tests can be used to diagnose pyruvate kinase deficiency. Blood tests such as a complete blood count and a bilirubin test can help identify abnormal levels of red blood cells and bile in the blood. Genetic tests can identify mutations in the PKLR gene. Pyruvate kinase activity can also be analyzed to detect abnormal levels in the body, according to the University of Maryland Medical Center. The signs and symptoms of anemia may also help in the diagnosis of pyruvate kinase deficiency.
Treatment
No specific treatment exists for pyruvate kinase deficiency, and therapy is largely dependent on the severity of the disease and resulting anemia. In more severe cases of anemia, individuals may need blood transfusions to replenish red blood cells. Surgically removing the spleen, which breaks down and removes red blood cells and other waste from the blood, may help reduce the destruction of red blood cells, according to the University of Maryland Medical Center.
References
- University of Maryland Medical Center: Pyruvate kinase deficiency - Overview
- Blut: Pyruvate Kinase-Catalyzed ATP-Formation in Humand Red Blood Cell Membranes
- National Heart, Lung and Blood Institute: What Is Hemolytic Anemia?
- The Franklin Institute: Red Blood Cells: Riding on the Red Road
- The Hematology Journal: Pyruvate Kinase Deficiency
