Final answer:
A Hemoglobin F (HbF) concentration of 100% is not typically seen in β-thalassemia, but rather in infants or other conditions like hereditary persistence of fetal hemoglobin (HPFH). β-thalassemia involves mutations in the β-globin gene leading to decreased synthesis of β-globin chains. A 100% HbF concentration would be highly atypical for β-thalassemia.
Step-by-step explanation:
Hemoglobin F Concentration in Beta Thalassemia
Hemoglobin F (HbF) concentration of 100% is not typically observed in β-thalassemia, but rather in infants or in conditions such as hereditary persistence of fetal hemoglobin (HPFH). In β-thalassemia, there is a mutation in the β-globin chain of hemoglobin, which leads to its decreased synthesis. This, in turn, can result in a compensatory increase in HbF, but rarely to 100%. The hallmark of β-thalassemia is the presence of hypochromic microcytic anemia, with varying degrees of HbF elevation, but it is not usually complete. Therefore, while increased levels of HbF may be seen in β-thalassemia, a concentration of 100% would be extremely atypical and suggests another diagnosis.
A mutation in the promoter region of the β-globin gene can lead to β-thalassemia. Since the promoter region controls the transcription of the gene into mRNA, mutations here can reduce or eliminate the production of β-globin chains. With insufficient β-globin chains, there is an imbalance in the ratio of alpha to β chains, leading to the formation of unstable hemoglobin molecules and the associated clinical symptoms of thalassemia.