A CBC shows bite cells on the smear and supravital staining revealing dark membrane inclusions. LDH is markedly elevated and DAT is negative. Which enzyme deficiency is most likely?

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Multiple Choice

A CBC shows bite cells on the smear and supravital staining revealing dark membrane inclusions. LDH is markedly elevated and DAT is negative. Which enzyme deficiency is most likely?

Bite cells with dark inclusions on supravital staining point to oxidative damage to hemoglobin and its removal by the spleen. Those dark inclusions are Heinz bodies, formed when hemoglobin is denatured under oxidative stress. In this setting, the red blood cells have trouble defending against oxidative insults because of a deficiency in an enzyme that helps maintain glutathione in its reduced form. G6PD deficiency is the classic cause: the enzyme normally generates NADPH, which keeps glutathione reduced and protects hemoglobin from oxidative damage. When G6PD is deficient, oxidative stress (from drugs, infections, certain foods) leads to Heinz body formation, splenic pitting removes them resulting in bite cells, and hemolysis ensues, elevating LDH. The direct antiglobulin test is negative because this is a non-immune process, not an autoimmune destruction of red cells. Pyruvate kinase deficiency causes chronic hemolytic anemia due to ATP depletion in RBCs, but it does not typically produce Heinz bodies or bite cells with supravital stain. So the findings described most strongly support G6PD deficiency rather than PK deficiency.

Bite cells with dark inclusions on supravital staining point to oxidative damage to hemoglobin and its removal by the spleen. Those dark inclusions are Heinz bodies, formed when hemoglobin is denatured under oxidative stress. In this setting, the red blood cells have trouble defending against oxidative insults because of a deficiency in an enzyme that helps maintain glutathione in its reduced form.

G6PD deficiency is the classic cause: the enzyme normally generates NADPH, which keeps glutathione reduced and protects hemoglobin from oxidative damage. When G6PD is deficient, oxidative stress (from drugs, infections, certain foods) leads to Heinz body formation, splenic pitting removes them resulting in bite cells, and hemolysis ensues, elevating LDH. The direct antiglobulin test is negative because this is a non-immune process, not an autoimmune destruction of red cells.

Pyruvate kinase deficiency causes chronic hemolytic anemia due to ATP depletion in RBCs, but it does not typically produce Heinz bodies or bite cells with supravital stain. So the findings described most strongly support G6PD deficiency rather than PK deficiency.

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