Similar subsetting of the SCD cohort to just those individuals with a hemoglobin SS (Hb SS) homozygous genotype, which is the most common SCD genotype, showed no significant difference in prevalence of CH between Hb SS SCD and unaffected individuals (OR = 1.34, P = 0.22; Supplemental Figure 4). Here, GSTM1 is linked to cyclic hematopoiesis.