HBB and sickle cell disease: For example, the African specific (∼91% of the carriers) HBB c.20A > T (rs334) variant, is a known recessive pathogenic variant which causes sickle-cell disease (MIM:603903) (Ashley-Koch et al., 2000), but it is present in four African individuals (who could have sickle-cell disease) in a homozygous state in gnomAD.