G6PD Deficiency: The Daily PANCE Blueprint
A 24-year-old man of Mediterranean descent started trimethoprim-sulfamethoxazole three days ago for a urinary tract infection. He now has fatigue, scleral icterus, and dark cola-colored urine. Hemoglobin is 8.9 g/dL, down from 14.2 g/dL last month. The reticulocyte count and LDH are elevated, haptoglobin is undetectable, and indirect bilirubin is high. The peripheral smear shows bite cells and Heinz bodies. Which of the following is the most likely diagnosis?
A. Hereditary spherocytosis
B. Autoimmune hemolytic anemia
C. Sickle cell disease
D. Glucose-6-phosphate dehydrogenase (G6PD) deficiency
E. Beta thalassemia
Answer and topic summary
The answer is D. Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Acute hemolysis triggered by an oxidant drug, with bite cells and Heinz bodies on the smear, is glucose-6-phosphate dehydrogenase (G6PD) deficiency — an X-linked enzyme defect that leaves red cells unable to regenerate glutathione and defend against oxidative stress. Hemoglobin denatures into Heinz bodies, the spleen plucks them out, and the resulting bite cells are the fingerprint. Classic triggers are sulfa drugs, nitrofurantoin, dapsone, antimalarials, fava beans, and infection. The subtle trap: an enzyme assay drawn during the acute episode can be falsely normal, because the oldest, most deficient cells have already lysed and the surviving reticulocytes are enzyme-rich — retest several weeks later. Spherocytes with a positive Coombs would point to autoimmune hemolysis, spherocytes with a negative Coombs to hereditary spherocytosis, sickled cells to sickle cell disease, and target cells with lifelong microcytosis to thalassemia.
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