Pyruvate kinase deficiency

Pyruvate kinase deficiency is an inherited condition in which red blood cells break down earlier than they should. The medical term for that is chronic hemolytic anemia — “hemolytic” meaning red cells being destroyed, “anemia” meaning too few of them left to carry oxygen well.

Pyruvate kinase is an enzyme, a protein that drives a chemical reaction. Inside a red blood cell it sits at the narrowest point of the only route that cell has for making energy. Mature red cells have no mitochondria, so there is no backup pathway — if this one step is slow, the whole cell runs short.

Short of energy, the cell cannot keep its membrane in order or stay flexible. It stiffens, and the spleen — the organ that filters blood — pulls it out of circulation early.

This is a disorder of red cell chemistry. It is not a cancer, and it is not bone marrow failure: the marrow works perfectly well, but the cells it makes wear out too fast.

The severity range is unusually wide, wider than most conditions in this library. It runs from fluid build-up in an unborn baby at the severe end, through transfusion dependence from birth, to a mild form noticed only in adulthood — or never noticed at all. Symptoms also do not track the hemoglobin number reliably: two people with similar blood counts can feel very differently.

It is caused by changes in the PKLR gene, which carries the instructions for the form of pyruvate kinase used in red cells and the liver.

Inheritance is autosomal recessive: a person must inherit an altered copy from each biological parent. Carriers with one altered copy typically have no symptoms at all. Where both parents are carriers, each pregnancy carries a 1-in-4 chance of an affected child.

Nothing a parent did or did not do causes it. It is not acquired, not contagious and not related to lifestyle.

Hundreds of different changes in that gene exist, and which particular pair someone carries matters — it influences both how severe the condition is and whether the targeted drug is likely to work for them.

It occurs in all ethnic groups, and is notably more common in the Old Order Amish population of Pennsylvania, which carries a distinct founder variant.

The core effects come from red cells being destroyed faster than they are replaced: pallor, fatigue, breathlessness, a fast heartbeat, and jaundice — yellowing of the eyes and skin from bilirubin, the pigment released when red cells break down.

The newborn period is often where it first shows. In an international registry of children with the condition, the large majority had newborn jaundice, most needed light treatment for it, and a third needed an exchange transfusion.

Gallstones are the classic downstream problem, because excess bilirubin forms pigment stones. In that same registry the rate climbed sharply with age, and a substantial minority of children had already had their gallbladder removed. The spleen also enlarges, from working overtime clearing damaged cells.

Then the thing that surprises people: iron overload happens here regardless of transfusions. It occurs in people who have never been regularly transfused, because ongoing red cell breakdown itself drives the gut to absorb more iron. Excess iron accumulates in the liver, heart and hormone glands, and it is silent until it causes damage — which is why monitoring is advised for everyone with the condition, not only those being transfused.

Less common but documented: reduced bone density, blood production outside the marrow sometimes forming masses beside the spine, leg ulcers, and raised pressure in the lung arteries. Anemia can also worsen temporarily during infections and during pregnancy.

There is no single standard treatment. Care is matched to how severe the condition is, and many people need supportive care only. This page cannot say what any individual will need.

Transfusions are occasional for some people and regular and lifelong for others. Expert reviews describe those decisions as driven by symptoms rather than by a fixed hemoglobin threshold.

Removing the spleen reduces where the red cells are being destroyed. It usually improves the anemia without normalising it — around 15% of people remain regularly transfused afterward — and it carries permanent trade-offs, including a lifelong raised risk of severe infection and a documented risk of blood clots. Reviews describe delaying it until at least age five where that is possible. Gallbladder removal is common and is sometimes done in the same operation.

Iron is monitored and, where needed, removed with chelation medicines — including in people who were never regularly transfused. Folic acid supplementation is standard supportive practice in any chronic hemolysis.

Mitapivat, sold as Pyrukynd, is an oral drug that makes the faulty enzyme work better. It was approved in the US in 2022, and the indication is narrow: hemolytic anemia in ADULTS with pyruvate kinase deficiency. The label states that safety and effectiveness in children have not been established. Eligibility also depends on genotype — the trial required at least one particular class of gene change, and people with certain variant combinations were excluded because earlier work showed they did not respond.

Most people arrive at this subject having never heard the name. Many were told they or their child had “a rare enzyme problem” and left to search for it. Naming the thing plainly is most of what a page like this can usefully do.

Diagnosis is often delayed in milder cases, and some adults find out only after years of unexplained tiredness, jaundice or gallstones.

For parents, the newborn phase can be intense — jaundice, light treatment, sometimes an exchange transfusion — followed by a long stretch of hospital visits and transfusions through the first years. In the children’s registry, regular transfusion was much more common under age five than in the teenage years.

Day to day, fatigue and jaundice are the burden. Visible jaundice is described in the literature as psychologically significant for children and adolescents, and that is a real quality-of-life matter rather than a cosmetic one.

The decisions families face are genuinely difficult and are made with a haematologist: whether and when to remove the spleen, whether to transfuse regularly, how to manage iron.

Very little, and it is worth saying that directly rather than leaving it to be inferred. A transplant is not the usual route for pyruvate kinase deficiency. A worldwide study identified 16 people who had received an allogeneic transplant for it across roughly two decades, at a median age of six and a half.

That series reported serious harm — severe graft-versus-host disease and transplant-related deaths — and its authors concluded that being dependent on transfusions alone should not be an indication for a transplant. A 2020 expert review recommended continuing supportive care with spleen removal and transfusions rather than transplant for the majority of people. A more recent review positions it as something to consider for severe disease with a high transfusion burden despite drug treatment and spleen removal.

Where a transplant is done, it uses blood-forming cells from another person — a matched family member or an unrelated volunteer found through a registry. And because the condition is recessive, brothers and sisters may themselves be affected or be carriers, so a family match cannot be assumed.