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Embden-Meyerhof Pathway Defects

By Evan M. Braunstein, MD, PhD, Assistant Professor of Medicine, Division of Hematology, Department of Medicine, Johns Hopkins School of Medicine

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Embden-Meyerhof pathway defects are autosomal recessive RBC metabolic disorders that cause hemolytic anemia.

The most common defect is

  • Pyruvate kinase deficiency

Other defects that cause hemolytic anemia include deficiencies of

  • Erythrocyte hexokinase

  • Glucose phosphate isomerase

  • Phosphofructokinase

In all of these pathway defects, hemolytic anemia occurs only in homozygotes. The exact mechanism of hemolysis is unknown. Symptoms are related to the degree of anemia and may include jaundice and splenomegaly. Spherocytes are absent, but small numbers of irregularly shaped spheres may be present.

In general, assays of ATP and diphosphoglycerate help identify any metabolic defect and localize the defective sites for further analysis.

Treatment

  • Supportive care

  • Sometimes splenectomy

There is no specific therapy for these hemolytic anemias. Most patients require no treatment other than supplemental folate 1 mg po once/day during acute hemolysis. In severe cases, patients may be transfusion dependent in which case, splenectomy may be done. Hemolysis and anemia persist after splenectomy, although some improvement may occur, particularly in patients with pyruvate kinase deficiency.