Fetal Haemoglobin Production and the Sickle Gene in the Oases of Eastern Saudi Arabia

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Abstract
Fetal Hb (Hb F) levels were measured in 137 normal (AA) subjects, 109 with the sickle-cell trait (AS) and 237 with sickle-cell anemia (SS) from the oasis population of Eastern Saudi Arabia. The proportion of F [erythrocytes containing Hb F] cells was estimated in 71 AA, 51 AS and 34 SS subjects. The mean Hb F% (and the range of F cells %) were AA 0.77 (0.3-18), AS 1.38 (2.3-43) and SS 25.56 (33-98). The distribution of Hb F was always heterocellular. The influence of pregnancy accounted for most of the excess female subjects with sickle-cell trait showing raised Hb F and F cells. While normal Arabs and those with sickle-cell trait did not differ from comparable groups of American blacks, the percent Hb F and percent F cells in Saudi Arabian patients with sickle-cell anemia were much higher than in blacks. The high Hb F levels in individuals with sickle-cell anemia were not due to coexistent glucose-6-phosphate dehydrogenase deficiency or .alpha.-thalassemia trait. The Hb F level showed an inverse correlation with degree of hemolysis. The unusually elevated levels of Hb F were apparently not due to an associated high frequency of a gene for hetero-cellular hereditary persistence of fetal Hb in the oasis population, but from a genetically determined absolute increase in Hb F production related in some way to the SS genotype.