The Interaction of Alpha-Thalassemia and Homozygous Sickle-Cell Disease

Patients with homozygous sickle-cell disease may be homozygous for alpha-thalassemia 2 (α–/α–), may be heterozygous for alpha-thalassemia 2 (α–/αα), or may have a normal alpha-globin-gene complement (αα/αα). We compared the clinical and hematologic features of 44 patients who had sickle-cell disease and homozygous alpha-thalassemia 2 with those of controls with the two hematologic conditions. The patients with homozygous alpha-thalassemia 2 had significantly higher red-cell counts and levels of hemoglobin and hemoglobin A2, as well as significantly lower hemoglobin F, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean corpuscular volume, reticulocyte counts, irreversibly-sickled-cell counts, and serum total bilirubin levels, than those with a normal alpha-globin-gene complement. Heterozygotes (α–/αα) had intermediate values. In the group with homozygous alpha-thalassemia 2, fewer patients had episodes of acute chest syndrome and chronic leg ulceration and more patients had splenomegaly, as compared with patients in the other two subgroups. These data confirm previous suggestions that alphathalassemia inhibits in vivo sickling in homozygous sickle-cell disease and may be an important genetic determinant of its hematologic severity. (N Engl J Med. 1982; 306: 1441–6.), HETEROZYGOUS alpha-thalassemia 2 is now known to have a high prevalence in black populations and would therefore be expected to occur in association with homozygous sickle-cell disease. Alpha-thalassemia lowers mean cell volume and intracellular hemoglobin concentration, and both these changes might be expected to be beneficial to patients with sickle-cell disease. Previous reports of the association of these two conditions have been anecdotal, conflicting, based on small samples of patients or lacking in appropriate control observations.12345678910 In the present report the clinical and hematologic features of 44 patients with sickle-cell disease in whom restriction-endonuclease studies indicated homozygous alpha-thalassemia 2 are. © 1982, Massachusetts Medical Society. All rights reserved.