The sickle cell gene is widely distributed among populations of southern Europe, the Middle East, and India, reflecting diffusion of African genetic material during a millennium or more of the east African slave trade. Mild homozygous sickle cell disease, reported among Eti-Turks and Arabs from Kuwait and Saudi Arabia, may in part represent favorable interaction between sickle cell disease and α-thalassemia or hemoglobin H disease. Favorable interaction between glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and sickle cell disease, in populations where high frequencies of the enzyme defect and the sickle cell trait coexist, has been postulated but certainly not established. A better understanding of sickle cell disease may be afforded by further studies of the problem in populations with high frequencies of the thalassemia traits and G-6-PD deficiency occurring in association with sickle cell disease.
Gelpi AP, Perrine RP. Sickle Cell Disease and Trait in White Populations. JAMA. 1973;224(5):605-608. doi:10.1001/jama.1973.03220180029007