Unstable hemoglobins are prone to oxidative denaturation even in the presence of a normal G6PD system. The disorder is autosomal dominant and of variable severity. Most patients have a mild chronic hemolytic anemia with splenomegaly, mild jaundice, and pigment (calcium bilirubinate) gallstones. Less severely affected patients are not anemic except under conditions of oxidative stress.
The diagnosis is suspected by the finding of Heinz bodies combined with a normal G6PD level when checked during a period of hemolytic quiescence. Hemoglobin electrophoresis is usually normal, since these hemoglobins characteristically do not have a change in their migration pattern. These hemoglobins precipitate in isopropanol. Usually no treatment is necessary. Patients with chronic hemolytic anemia should receive folic acid supplementation (1 mg orally) and avoid known oxidative drugs. In rare cases, splenectomy may be required.
et al. Gene therapy approaches to hemoglobinopathies. Hematol Oncol Clin North Am. 2017 Oct;31(5):835–52.