Dapsone and Heinz Bodies

To the Editor.—  Dapsone (4,4′-diaminodiphenylsulfone) causes dose-limiting hemolysis and methemoglobinemia, with formation of Heinz bodies (denatured hemoglobin particles) and characteristic poikilocytes.¹ It has been proposed that Heinz body testing during dapsone treatment might be useful²; we have found it to be of restricted value.Twelve clinically stable, nonsplenectomized patients with normal erythrocyte glucose-6-phosphate dehydrogenase levels³ had been treated with constant dosage of dapsone for various skin disorders for at least one month. Mean (±SD) daily drug dosage was 122 (±69) mg. Complete blood cell counts, methemoglobin levels,⁴ reticulocyte counts,⁵ and Heinz body quantifications⁶ were performed two to four times (mean interval [±SD], 6.9 ± 5.7 weeks, minimum interval, one week, 35 studies).Normal values used for hemoglobin levels, reticulocyte count, methemoglobin levels, and Heinz body counts are 13 to 17 g/dL, 25,000 to 75,000/cu mm, less than 1.0%, and none detected, respectively. Respective mean