The PKLR gene gives instructions for an enzyme that helps red blood cells make usable energy from sugar. This gene helps your body keep red blood cells flexible and working normally, so if it does not work well, the cells can break down too soon. People with pathogenic variants in the PKLR gene may develop pyruvate kinase deficiency, which can lead to anemia, tiredness, jaundice, gallstones, or an enlarged spleen.
What is a gene?
A gene is a stretch of DNA that holds instructions your cells use to make molecules or manage processes in the body. Some genes carry the directions for producing proteins, the parts of cells that do much of the work. Others mainly help regulate when certain processes happen, where they happen, and how strongly they occur. Together, genes affect how the body develops and works, and they can shape how you respond to food, stress, or medications. If you want to go into this topic in greater depth, you can read more in the LearnHub.
Overview
PKLRGene function
What if the gene works
The PKLR gene helps red blood cells and liver cells turn sugar into usable energy. This supports oxygen delivery and the liver’s everyday energy needs.
Risk
What if the gene does not work
Variants in the PKLR gene can cause pyruvate kinase deficiency, where red blood cells break down too soon and cause anemia. Effects range from mild to severe and may appear from birth or later in life.
Treatment
What does that mean for your treatment
Pathogenic variants in the PKLR gene can affect whether mitapivat is likely to help. Because this drug activates the pyruvate kinase enzyme, people who still make some altered enzyme may respond better, while those with two loss-of-function variants, which stop the enzyme from working, are less likely to benefit. Other care, including transfusions or splenectomy, is guided mainly by symptoms rather than the exact variant.
Conditions associated with PKLR
Gene function
What if the gene works
Your cells use the PKLR gene to turn part of the sugar you eat into usable energy. It provides instructions for pyruvate kinase, an enzyme that carries out a key last step in glycolysis, the body’s main way of breaking down glucose. This is an important part of how the PKLR gene helps red blood cells make energy and supports normal liver metabolism.
The PKLR gene helps complete the last major step of glycolysis. Its enzyme changes phosphoenolpyruvate into pyruvate and makes ATP, the cell’s direct energy source.
In red blood cells, this pathway provides most of the energy used for daily upkeep. That steady ATP supply helps these cells hold their shape and move through very small blood vessels.
In the liver, PKLR supports normal handling of glucose from food. It helps the liver decide when sugar is used for energy and when it is directed into storage or other routine metabolic work.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These differences are common and help shape normal human diversity, including variation in appearance, metabolism, and how the body responds to environmental influences. Many have no noticeable effect and are simply part of natural genetic variation. In some cases, however, a variant can change how a gene works more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
In the PKLR gene, some variants slightly reduce the pyruvate kinase enzyme’s stability or activity, while others greatly lower how much enzyme is made or create a shortened protein that works poorly. This helps explain how PKLR gene variants affect pyruvate kinase deficiency: milder changes may leave some enzyme activity, while more severe variants can leave very little. When activity is lower, symptoms often start earlier and may be more noticeable.
How variants are linked to conditions
Pathogenic variants in the PKLR gene cause pyruvate kinase deficiency, an inherited condition best known for ongoing hemolytic anemia, where red blood cells break down sooner than usual. Some people have mild symptoms, while others may develop jaundice, gallstones, tiredness, or an enlarged spleen. Severity can vary widely among people with PKLR gene variants and pyruvate kinase deficiency.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are widely found in the general population. Most do not have a direct effect on health and instead reflect normal human diversity. For many genes, having a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when multiple genes and environmental factors also play a role. In some situations, though, a single well-characterized variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For PKLR, the main factor is inheritance: the chance of having PKLR-related anemia is much higher when both parents carry a changed PKLR gene, so family history can strongly affect risk. In people already living with this condition, infections, pregnancy, and other stresses on the body can make anemia and jaundice worse.
Inheritance of PKLR variants
PKLR-related pyruvate kinase deficiency follows an autosomal recessive inheritance pattern. This means a child inherits one PKLR gene variant from each parent, and parents who each carry one variant usually do not have the condition themselves. When both parents are carriers, each pregnancy has a 25% chance of a child having the condition, a 50% chance of a child being a carrier, and a 25% chance of inheriting neither variant. Sons and daughters are affected equally because the PKLR gene is on an autosome, not a sex chromosome.
What does my PKLR result mean for my family?
For families with a disease-causing PKLR result, brothers and sisters may also be affected or may carry the same gene change, even if they feel well. Parents are often healthy carriers, and other relatives can be carriers too. This can matter for future children in the family, because two carriers can have a child with pyruvate kinase deficiency.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry a change in the PKLR gene, doctors use genetic testing for PKLR gene variants on a blood or saliva sample. A lab reads the gene’s DNA code and looks for variants that may help explain ongoing anemia or show whether relatives carry the same variant.
When should I consider getting a genetic test?
Consider PKLR genetic testing if you or your child has ongoing anemia from red blood cells breaking down too quickly, especially with jaundice, gallstones, an enlarged spleen, or a family history of pyruvate kinase deficiency. Testing can confirm the cause and help clarify whether close relatives may also carry the gene change.
A genetic result is only one part of your health story
Genetic results can be informative, but how much they reveal varies with the condition and the kind of variant involved. Over time, the way the body works is also shaped by many other factors, including lifestyle, environment, age, and medical history. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is most useful when considered alongside other aspects of care. In other situations, a genetic result can provide a clear answer. In areas like medication response, these results can also help place individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can influence how people respond to medicines. Small inherited differences can affect how the body breaks down a drug, moves it through the body, or responds to it where it is meant to work. This helps explain why the same treatment may work well for one person, work less well for another, or cause more side effects in someone who is more sensitive to it.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can affect a person’s response to medications. It studies patterns between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes influence how strongly a drug works or how the body handles it. This information can support treatment decisions that are more informed and more individualized. More on this topic is available in the LearnHub.
Drugs influenced by the PKLR gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice or dose, so general health or medicine concerns are best discussed with your doctor. Research on PKLR mainly relates to treatments for pyruvate kinase deficiency, where the exact gene change may affect whether a newer treatment is likely to help.
History
The PKLR gene entered medical history through studies of families with a long recognized inherited anemia, now called pyruvate kinase deficiency. First described in the scientific literature as part of early genetics, this condition helped establish that some anemias come from changes inside red blood cells rather than from blood loss or immune causes. In the 1960s, researchers linked the illness to low pyruvate kinase activity in red blood cells. Building on this early work, scientists identified the PKLR gene and mapped many different variants that can run in families. These discoveries made PKLR an important part of the history of inherited red blood cell conditions. Over time, descriptions became more precise as DNA testing replaced diagnosis based only on blood and enzyme studies.