Table 1 Categorization and sequelae of hemoglobinopathies examined
Category | Nomenclature | Definition; sequelae |
|---|---|---|
Normal hemoglobin (AA) or hemoglobin C trait (AC) | HbAA/AC | Red blood cells are normal, and individuals have no symptoms and normal hemoglobin concentrations [9, 15] |
Homozygous sickle cell genes | HbSS | Sickle cell gene inherited from both parents, resulting in red blood cells that have a sickle shape at low oxygen tension; HbSS can result in increased under-5 mortality and maternal mortality, and hemoglobin concentrations are often around 80 g/L [9, 16] |
Heterozygous sickle cell trait | HbSC | Heterozygous sickle cell trait, whereby individuals inherit a sickle cell gene from one parent and a hemoglobin C gene from the other parent; individuals have fewer sickle cells but may have slightly lower hemoglobin concentrations than HbAA individuals [17]. Hemoglobin C is most prevalence in West Africa [15] |
Heterozygous sickle cell trait | HbAS | Heterozygous sickle cell trait, whereby individuals inherit a normal hemoglobin A gene from one parent and a hemoglobin S gene (i.e. sickle cell gene) from the other parent; Individuals often no symptoms and normal hemoglobin concentrations [6] and inherit partial protection against malaria [18] |
β-Thalassemia | β-Thalassemia | An inherited mutation that results in a “reduced or absent synthesis of beta globin chains” [19]; red blood cells are smaller than usual and hemoglobin may be lower than in HbAA individuals [20] |