Pyruvate kinase deficiency (PK) is a rare enzyme disorder of the Embden-Meyerhof pathways. Red cells lacking this enzyme are unable to generate adenosine triphosphate (ATP) from adenosine diphosphate (ADP) for red cell membrane function. The result is rigid, inflexible cells that are sequestered by the spleen and hemolyzed. Both sexes are affected in this autosomal recessive disorder. There is a high incidence in individuals of northern European origin and in the close-knit Amish population of Mifflin County, Penn-sylvania.21 Patients show a moderate hemolysis with hematocrits of between 18% and 36%,22 with little abnormal morphology on the peripheral smear, save for marked polychromasia and a few nRBCs. A fluorescent screening test is used followed by a specific assay for PK activity.
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