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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Hematology · Pyruvate Kinase Deficiency

The Biology and Diagnosis of Pyruvate Kinase Deficiency (PKD)

At a Glance

Pyruvate Kinase Deficiency (PKD) is a genetic disorder where a PKLR gene mutation stops red blood cells from making enough energy, causing them to break down prematurely. Accurate diagnosis requires specialized testing like a PK-to-hexokinase ratio test and genetic sequencing.

To understand Pyruvate Kinase Deficiency (PKD), it helps to think of the red blood cell as a tiny vehicle that needs fuel to keep moving. In PKD, a genetic “glitch” prevents the vehicle from making the fuel it needs, causing it to break down long before its time [1][2].

The Biology: An Energy Crisis

The root of PKD lies in the PKLR gene, which provides the instructions for making the pyruvate kinase enzyme [3][4]. This enzyme is a key worker in glycolysis, the process red blood cells use to convert sugar into energy, known as ATP (adenosine triphosphate) [2][5].

Because red blood cells do not have a nucleus or other complex machinery, they rely entirely on glycolysis for energy [5]. When the pyruvate kinase enzyme is missing or broken:

  1. ATP levels drop: The cell cannot produce enough energy to maintain its shape and function [1][2].
  2. Cellular Exhaustion: Without energy, the cell’s “pumps” fail, causing it to lose water and potassium, making it fragile and rigid [2].
  3. Premature Destruction: The body’s filter (the spleen) recognizes these stiff, energy-depleted cells as “broken” and destroys them. While a normal red blood cell lives about 120 days, a cell with PKD may last only a few days or weeks [2][1].

How PKD Differs from Other Anemias

PKD is often mistaken for other types of hemolytic anemia (anemias where cells are destroyed), but the biological “why” is different:

Condition Biological “Glitch” Result
PKD Enzyme defect in glycolysis (energy pathway) [5]. Red cells run out of energy and “die” early [2].
G6PD Deficiency Enzyme defect in the antioxidant pathway [6]. Red cells are destroyed only when exposed to “stressors” like certain foods or infections [6].
Hereditary Spherocytosis Defect in the cell’s outer “shell” (membrane proteins) [7]. Red cells become sphere-shaped and get stuck in the spleen [8].

Making a Definitive Diagnosis

Because PKD is rare and its symptoms overlap with other conditions, doctors use two primary methods to confirm it.

1. The PK:Hexokinase Ratio

Measuring the pyruvate kinase (PK) enzyme alone can be tricky. This is because young red blood cells (reticulocytes) naturally have higher enzyme levels than older cells. Since PKD patients produce many young cells to compensate for anemia, a standard test might look “normal” even when a deficiency exists [9].

To solve this, doctors measure both PK and another enzyme called hexokinase. Since both are high in young cells, the PK:hexokinase ratio provides a much more accurate picture. A low ratio has been shown to be nearly 100% sensitive for identifying PKD [9].

2. Genetic Testing (NGS)

Next-Generation Sequencing (NGS) is a highly detailed blood test that looks directly at the PKLR gene [10][11]. It is the most definitive way to confirm the diagnosis, especially if enzyme tests are unclear [12].

Reading Your Lab Reports

Because diagnosis requires multiple methods, you will likely receive two different types of lab reports. Understanding them helps you verify the accuracy of your diagnosis.

Reading Your Enzyme Assay Report

  • Leukocyte-Depletion: Check if the report mentions that white blood cells were removed before testing. White blood cells have their own pyruvate kinase, and if they aren’t removed, they can “hide” a deficiency in the red blood cells [13].
  • PK:Hexokinase Ratio: A low ratio points heavily toward PKD, as it correctly accounts for the age of the red blood cells [9].

Reading Your Genetic Test Report

  • PKLR Mutation: The report should list two mutations (e.g., c.1529G>A). Because PKD is autosomal recessive, you typically need two mutations (one from each parent) to have the disease [14][15].
  • Variant Type: You may see terms like missense (a “spelling error” that changes one part of the enzyme) or non-missense (a more severe error that stops enzyme production entirely) [11][16].

Common questions in this guide

What causes Pyruvate Kinase Deficiency (PKD)?
PKD is caused by mutations in the PKLR gene, which provides instructions for making an enzyme called pyruvate kinase. Without enough of this enzyme, red blood cells cannot produce the energy they need to survive, leading to their early destruction.
Why is the PK-to-hexokinase ratio used to diagnose PKD?
Standard enzyme tests can sometimes look normal in PKD patients because their bodies produce many young red blood cells, which naturally have higher enzyme levels. Measuring the ratio of pyruvate kinase to hexokinase accounts for these young cells and provides a much more accurate diagnosis.
Why do my lab results mention leukocyte depletion?
White blood cells (leukocytes) have their own supply of pyruvate kinase. If they are not removed from the blood sample before testing, they can mask the deficiency in your red blood cells and cause a false normal result.
What does an autosomal recessive diagnosis mean for PKD?
Autosomal recessive means you must inherit two mutated copies of the PKLR gene—one from each parent—to develop the disease. Your genetic test report will typically list two specific mutations if you have PKD.
How is PKD different from other types of hemolytic anemia like G6PD?
While both cause red blood cells to break down, they have different biological triggers. PKD is a constant energy crisis within the cell, whereas G6PD deficiency only causes cell destruction when the body is exposed to specific stressors like certain foods or infections.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was the blood sample for my (or my child's) enzyme test 'leukocyte-depleted' to ensure the white blood cells didn't skew the results?
  2. 2.What was the exact PK:hexokinase ratio, and how does it compare to the normal range?
  3. 3.Do the genetic results show 'homozygous' (two identical mutations) or 'compound heterozygous' (two different mutations) changes in the PKLR gene?
  4. 4.Based on the specific mutations found, is the disease likely to be classified as mild, moderate, or severe?
  5. 5.Were there any signs of 'reticulocytosis' (high young red blood cell count) that could have made the initial enzyme test look more normal than it actually is?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
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    Boscoe AN, Yan Y, Hedgeman E, et al.

    European journal of haematology 2021; (106(4)):484-492 doi:10.1111/ejh.13572.

    PMID: 33370479
  2. 2

    Worldwide study of hematopoietic allogeneic stem cell transplantation in pyruvate kinase deficiency.

    van Straaten S, Bierings M, Bianchi P, et al.

    Haematologica 2018; (103(2)):e82-e86 doi:10.3324/haematol.2017.177857.

    PMID: 29242305
  3. 3

    Pyruvate kinase L/R is a regulator of lipid metabolism and mitochondrial function.

    Liu Z, Zhang C, Lee S, et al.

    Metabolic engineering 2019; (52()):263-272 doi:10.1016/j.ymben.2019.01.001.

    PMID: 30615941
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    Pyruvate kinase deficiency in children.

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    Pediatric blood & cancer 2021; (68(9)):e29148 doi:10.1002/pbc.29148.

    PMID: 34125488
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    Compound heterozygosity in PKLR gene for a previously unrecognized intronic polymorphism and a rare missense mutation as a novel cause of severe pyruvate kinase deficiency.

    Bagla S, Bhambhani K, Gadgeel M, et al.

    Haematologica 2019; (104(9)):e428-e431 doi:10.3324/haematol.2018.214692.

    PMID: 30948487
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    Genetic analysis and molecular basis of G6PD deficiency among malaria patients in Thailand: implications for safe use of 8-aminoquinolines.

    Boonyuen U, Jacob BAC, Wongwigkan J, et al.

    Malaria journal 2024; (23(1)):38 doi:10.1186/s12936-024-04864-8.

    PMID: 38308253
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    Detection of red blood cell antibodies in mitogen-stimulated cultures from patients with hereditary spherocytosis.

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    Transfusion 2015; (55(12)):2930-8 doi:10.1111/trf.13257.

    PMID: 26259504
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    Long-term follow-up of subtotal splenectomy for hereditary spherocytosis: a single-center study.

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    Blood 2016; (127(12)):1616-8 doi:10.1182/blood-2015-11-679357.

    PMID: 26773041
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    Pyruvate kinase deficiency in 29 Turkish patients with two novel intronic variants.

    Gök V, Leblebisatan G, Gürlek Gökçebay D, et al.

    British journal of haematology 2024; (205(1)):236-242 doi:10.1111/bjh.19575.

    PMID: 38811201
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    Expanding the PKLR mutation spectrum: discovery of two novel variants in two pediatric cases of pyruvate kinase deficiency.

    Sakalian O, Huguenin Y, Pissard S, et al.

    Annals of hematology 2026; (105(7)).

    PMID: 42115487
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    Novel PKLR missense mutation (A300P) causing pyruvate kinase deficiency in an Omani Kindred-PK deficiency masquerading as congenital dyserythropoietic anemia.

    Fawaz N, Beshlawi I, Alqasim A, et al.

    Clinical case reports 2022; (10(2)):e05315 doi:10.1002/ccr3.5315.

    PMID: 35154711
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    Pyruvate kinase deficiency mimicking congenital dyserythropoietic anemia type I.

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    The Turkish journal of pediatrics 2022; (64(5)):951-955.

    PMID: 36305449
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    Diagnosis of Pyruvate Kinase Deficiency.

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    Pediatric blood & cancer 2016; (63(5)):771-2 doi:10.1002/pbc.25922.

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    Prevalence of pyruvate kinase deficiency: A systematic literature review.

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    European journal of haematology 2020; (105(2)):173-184 doi:10.1111/ejh.13424.

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    Neonatal Thrombocytopenia as a Presenting Finding in de novo Pyruvate Kinase Deficiency.

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    Targeted next-generation sequencing identifies eighteen novel mutations expanding the molecular and clinical spectrum of PKLR gene disorders in the Indian population.

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This page is for informational purposes only and does not replace professional medical advice. Always consult your hematologist or genetic counselor for interpreting your specific diagnostic lab results.

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