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Sickle cell disease is common in some ethnic groups of central India, [168] where the prevalence has ranged from 9.4 to 22.2% in endemic areas of Madhya Pradesh, Rajasthan, and Chhattisgarh. [169] It is also endemic among Tharu people of Nepal and India; however, they have a sevenfold lower rate of malaria despite living in a malaria infested ...
The sickle cell trait provides a survival advantage against malaria fatality over people with normal hemoglobin in regions where malaria is endemic. The trait is known to cause significantly fewer deaths due to malaria, especially when Plasmodium falciparum is the causative organism.
For example, people of African American ethnicity have a much higher likelihood of being a carrier for the autosomal recessive disorder called sickle cell anemia. [3] People of one ethnicity in particular, Ashkenazi Jewish, have a tendency to be carriers for a wide variety of recessive genetic disorders. There are also several recessive ...
If he has microcytosis (mean cell hemoglobin < 27 pg or mean red cell volume < 80 fl), the woman is tested. When both are microcytic, their hemoglobin A2 concentrations are measured. If both have a concentration above 3.5% (diagnostic of thalassemia trait) they are referred to the local designated health post for genetic counseling .
Hemoglobin A2 (HbA 2) is a normal variant of hemoglobin A that consists of two alpha and two delta chains (α 2 δ 2) and is found at low levels in normal human blood.Hemoglobin A2 may be increased in beta thalassemia or in people who are heterozygous for the beta thalassemia gene.
This would be similar to the hemoglobin allele which is responsible for sickle-cell disease, but solely in people with two copies; those with just one copy of the allele have a sickle cell trait and gain partial immunity to malaria as a result. This effect is called heterozygote advantage. [27]
Red cell alloimmunisation is common in people with sickle cell disease who receive transfusions in Europe and North America. [4] This is because there are ethnic differences in the frequencies of blood group antigens. [4] Blood donors are usually Caucasian whereas the blood transfusion recipients usually have an African or Afro-Caribbean ancestry.
A similar relationship exists between malaria and sickle-cell disease. One theory to explain this is that cells infected with the Plasmodium parasite are cleared more rapidly by the spleen. This phenomenon might give G6PD deficiency carriers an evolutionary advantage by increasing their fitness in malarial endemic environments.