Hemoglobinopathy is a kind of genetic defect that results in abnormal structure of one of the globin chains of the hemoglobin molecule. Hemoglobinopathies are inherited single-gene disorders; in most cases, they are inherited as autosomal co-dominant traits.  Common hemoglobinopathies include sickle-cell disease. It is estimated that 7% of worlds population (420 million) are carriers, with 60% of total and 70% pathological being in Africa. Hemoglobinopathies are most common in ethnic populations from Africa, the Mediterranean basin and Southeast Asia.
Hemoglobinopathies imply structural abnormalities in the globin proteins themselves. Thalassemias, in contrast, usually result in underproduction of normal globin proteins, often through mutations in regulatory genes. The two conditions may overlap, however, since some conditions which cause abnormalities in globin proteins (hemoglobinopathy) also affect their production (thalassemia). Thus, some hemoglobinopathies are also thalassemias, but most are not.
Either hemoglobinopathy or thalasemia, or both, may cause anemia. Some well-known hemoglobin variants such as sickle-cell anemia are responsible for diseases, and are considered hemoglobinopathies. However, many hemoglobin variants do not cause pathology or anemia, and thus are often not classed as hemoglobinopathies, because they are not considered pathologies. Hemoglobin variants are a part of the normal embryonic and fetal development, but may also be pathologic mutant forms of hemoglobin in a population, caused by variations in genetics. Other variants cause no detectable pathology, and are thus considered non-pathological variants.
Hemoglobin (Hb;1 Mr 68 000) is the oxygen-carrying moiety of erythrocytes. It is a polypeptide tetramer, globular in structure, and consisting of two pairs of unlike globin chains (i.e., plus ß, , or ), which form a shell around a central cavity containing four oxygen-binding heme groups each covalently linked to a globin chain. In healthy adults, ~95% of the Hb is Hb A (2ß2) with small amounts (<3.5%) of Hb A2 (22) and Hb F (22) present. During embryonic development, "pre alpha" globin chains contribute to embryonic Hb. During fetal development, ß-like globin chains and contribute to the Hb (1).
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