General information

In healthy adults 97-98% of total hemoglobin (Hb) is HbA, consisting of two α-globin and wo β-globin polypeptides (α2β2). Abnormalities in the structure and synthesis of both globin chains lead to an imbalance causing the two main types of thalassemia: α-thalassemia and β-thalassemia. The loss of one of the two α-globin alleles (-α) on chromosome 16 causes α+-thalassemia, whereas α0-thalassemia is due to inactivation of both α-globin alleles (--). Two groups of β-globin mutations are distinguished, depending on whether they lead to a reduction (β+) or an absence (β0) of β-globin synthesis.In many regions, α- and β-thalassemia coexist with a variety of different structural Hb variants. These complex interactions give rise to an extremely wide spectrum of clinical phenotypes. Furthermore, an inherited increase of γ-globin expression in patients can partially compensate for the lack of normal β-globin chain synthesis in β-thalassemia as well as sickle cell disease and thereby can ameliorate the clinical phenotype of both disorders.

Numerous defects in the β-globin gene have been identified, many of which cause structural abnormalities, such as HbS (sickle cell hemoglobin), HbC, HbE, or lead to impaired β-globin synthesis, known as β-thalassemia. The clinical manifestations of the disease show a tremendous diversity, which correlates with the underlying genetic defects. β-Thalassemia major, the most severe and transfusion-dependent state, is characterized by the complete absence of HbA and results from the inheritance of two β0 alleles.

Individuals who have inherited a single β-thalassemia allele, whether β0 or β+, have β-thalassemia minor. They are often clinically asymptomatic but may have mild anemia with characteristic hypochromic microcytic red blood cells and elevated levels of HbA2 (α2δ2). The diverse phenotypes ranging between β-thalassemia major and β-thalassemia minor constitute the clinical syndrome of β-thalassemia intermedia, which in most cases results from the nheritance of either β+/β+ or β+/β0 alleles.

Sampling :  venous blood

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