Concurrent Sickle-Cell Anemia and α-Thalassemia: Effect on Severity of Anemia

We studied 47 patients with sickle-cell anemia to determine the effect of α-thalassemia on the severity of their hemolytic anemia. We diagnosed α-thalassemia objectively by using α-globin-gene mapping to detect α-globin-gene deletions, studying 25 subjects with the normal four α-globin genes, 18 with three, and four with two. The mean hemoglobin, hematocrit, and absolute reticulocyte levels (±S.D.) were 7.9±0.9 g per deciliter (4.9±0.6 mmol per liter), 22.9±2.9 per cent, and 501,000±126,000 per cubic millimeter, respectively, in the non-thalassemic group; 9.8±1.6 g per deciliter (6.1±1.0 mmol per liter), 29.0±5.0 per cent, and 361,000±51,000 per cubic millimeter in the group with three α-globin genes; and 9.2±1.0 g per deciliter (5.7±0.6 mmol per liter), 27.5±3.0 per cent, and 100,000±15,000 per cubic millimeter in the group with two α-globin genes. Deletion of α-globin genes was also accompanied by a decreased mean corpuscular hemoglobin concentration (MCHC) in post-reticulocyte erythrocytes and by increased hemoglobin F levels. The decreased intraerythrocytic hemoglobin S concentration and elevated hemoglobin F levels associated with α-thalassemia appear to diminish the degree of hemolytic anemia found in sickle-cell disease. (N Engl J Med. 1982; 306:270–4.) THE severity of hemolytic anemia, vaso-occlusive episodes, and end-organ failure in sickle-cell anemia varies widely among patients with the disease. Possible determinants of such variation include hemoglobin F levels 1 and concurrent α-thalassemia. 2 One would expect that the determinants most responsible for this variation would be widespread and would have diverse clinical consequences in the affected population. In this regard α-thalassemia is of particular interest, because it occurs in nearly one of three members of the American black population 3 and is associated with a variety of clinical syndromes. 4 , 5 Its favorable influence is presumably exerted through a reduction in the intracellular concentration . . .