John Old, in Emery and Rimoin's Principles and Practice of Medical Genetics, 2013
22.214.171.124 δβ-Thalassemia/Hb S
Hb S/δβ-thalassemia is a milder form of sickle-cell disease than sickle-cell anemia, because the high percentage of Hb F (15–25%) produced by the δβ-thalassemia allele protects against red cell sickling by reducing the Hb S concentration and inhibiting its polymerization. Hb S/δβ-thalassemia has been described in Sicilian, Italian, Greek, Arab, and African-American individuals. Patients have a mild anemia with a Hb concentration in the range of 10–12 g/dl, a significantly reduced MCH and MCV, Hb S, Hb F, and a normal or low Hb A2 level.