Cohorts’ description.

*Hb electrophoresis was also obtained from 344 patients (55.5%) using alkali denaturation test (ADT), with a mean of 11.4±9.4 for HbF and 4.1±2.1 for HbA2 levels. For the analysis, to correct for the skewness of the HbF distribution, we log10-transformed and normalized the data to obtain (after correcting for age, gender, and electrophoresis technique and history of transfusion) the quantitative trait used in the association analysis. NA = Not Applicable.