9.7: Pyruvate Kinase (PK) Deficiency

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: A peripheral blood smear with a pyknocyte* shown by the arrow (A). 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3VX06J4H

Normal PK Function:

Pyruvate Kinase catalyzes the conversion of phosphoenolpyruvate to pyruvate which results in the production of ATP from ADP. A lack of pyruvate kinase results in the ability of cells to maintain proper cell shape, normal lifespan, and low levels of 2,3-PBG.^1,2

Mutation:^1,2

Mutations in the PKLR gene leading to decreased levels of pyruvate kinase.

Inheritance:^1,2

Autosomal recessive

Complications:^1,2

Chronic hemolytic anemia

Splenomegaly

Jaundice

Gallstones

Notes:¹

WBCs contain more pyruvate kinase than RBCs.

Laboratory Results for PK Deficiency:¹

CBC:

Hb: Decreased

RETIC: Increased

*Note: The term “pyknocyte” is not universally used. It refers to a small, dehydrated, dark-colored RBC.

PBS:

Normocytic

Normochromic

Echinocytes

Pyknocytes*

Post-splenectomy shows varying degrees of anisocytosis and poikilocytosis

Other Tests:

Osmotic Fragility: Normal

Pyruvate Kinase Assay: Decreased

Indirect bilirubin: Increased

LDH: Increased

Haptoglobin: Decreased or absent

References:

1. Lake M, Bessmer D. Hemolytic anemia: enzyme deficiencies. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 334-47.

2. Keohane EM. Intrinsic defects leading to increased erythrocyte destruction. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 367–93.