Pyruvate kinase deficiency results in a glycolytic defect in red blood cells. A clinical suspicion needs to be verified by demonstrating low enzyme activity or a genetic defect.
Specialized testing:
(1) pyruvate kinase enzymatic activity in erythrocytes
(2) PK-LR gene testing
Indications for measuring pyruvate kinase enzymatic activity:
(1) unexplained chronic non-spherocytic hemolytic anemia (see below)
(2) transfusion dependent since birth without obvious cause
(3) unexplained severe neonatal hyperbilirubinemia
(4) reticulocytosis that increases after splenectomy
(5) family history of pyruvate kinase deficiency
Conditions in the differential diagnosis of pyruvate kinase deficiency:
(1) glucose-6-phosphatase deficiency (G6PD)
(2) hemoglobinopathy
(3) disorder of the red cell membrane (spherocytosis, etc)
(4) immune mediate hemolysis
Indications of gene testing:
(1) normal or low-normal pyruvate kinase activity with elevated activity of other age-dependent red blood cell enzymes
(2) chronically transfused patient whose assayed enzyme activity may be falsely normal
(3) low pyruvate kinase enzyme activity AND no family history
