Abstract
Hematological and hemoglobin composition data are presented for seven Arabian SS patients with mild disease and with high Hb F levels varying between 21 and 34%. Four patients were homozygous for a βS chromosome with a specific haplotype (#31). The data for these four patients were similar to those for three other SS patients (and for five patients reported earlier, Ref. 2) who were heterozygous for the same βS chromosome (#31) and for a βS chromosome with another haplotype (mainly #19). These data offer additional evidence indicating that the increased γ chain production is specific for the βS chromosome with haplotype #31. The similarities in hematological data and Hb F levels between these two groups of SS patients and the normal Hb F value in Hb S heterozygotes with βS chromosome (#31) support the suggestion that the increased Hb F production mainly occurs in response to the anemia of the sickle cell disease.