What is Sickle Cell Anemia?
Sickle cell anemia is a hereditary hemoglobinopathy associated with such a violation of the structure of the hemoglobin protein, in which it acquires a special crystalline structure – the so-called hemoglobin S. The red blood cells that carry hemoglobin S instead of normal hemoglobin A under the microscope have a characteristic sickle-shaped (sickle shape) , for which this form of hemoglobinopathy was called sickle cell anemia.
Sickle cell anemia is very common in malaria endemic regions of the world, and sickle cell anemia patients have an increased (although not absolute) congenital resistance to infection with various strains of malarial plasmodium. The sickle-shaped erythrocytes of these patients are also not susceptible to in vitro malaria plasmodium infection.
Causes of Sickle Cell Anemia
Sickle cell anemia is inherited in an autosomal recessive manner. In patients heterozygous for the sickle cell anemia gene, along with sickle-shaped erythrocytes that carry hemoglobin S, normal ones that carry hemoglobin A are also present in the blood. In this case, the disease is less clinically pronounced, it is easier, and sometimes it does not cause symptoms, and sickle-shaped red blood cells detected by chance in a laboratory study of blood. Homozygotes for the sickle cell anemia gene in the blood have only sickle red blood cells carrying hemoglobin S, and the disease is severe.
If both parents carry the sickle cell anemia gene, then their children are 25% likely to have sickle cell anemia and there is a 50% chance to inherit only their predisposition to it. If only one parent has the sickle cell anemia gene, there is absolutely no risk that the child will have sickle cell anemia, although there is a 50% chance that the child will inherit one sickle cell anemia gene.
Pathogenesis during Sickle Cell Anemia
The erythrocytes carrying hemoglobin S have reduced resistance and reduced oxygen transporting ability, therefore, in patients with sickle cell anemia, the destruction of red blood cells in the spleen is increased, their life is shortened, hemolysis is increased, and there are often signs of chronic hypoxia (oxygen deficiency) or chronic ” redistribution of erythrocyte bone marrow growth.