Sickle cell anemia–Causes-Symptoms-Diagnosis-Treatment–Prognosis

Sickle cell anemia (SCA) patients inherit two copies of the abnormal gene, one from each of their parents and hence it is known as a genetic or hereditary disease. The disease is passed on to the affected individual in an autosomal recessive mode of inheritance.

Those with the abnormal sickle cell gene produce abnormal hemoglobin which causes sickling of the RBCs.

If a person inherits a normal gene and a sickle cell gene from each parent, they are “carriers” of SCA. They have a condition called sickle cell trait, which is inherited in an autosomal dominant fashion. 8% of the African Americans have this condition at birth while in certain parts of Africa the prevalence is 5%. There are over 2 million Americans with sickle cell trait.


The carriers of sickle cell gene or sickle cell trait (heterozygote) do not manifest symptoms of SCA, and are able to lead normal lives. However, they are capable of passing on the deleterious genes to their children.

AA – Normal progeny has two copies of the normal gene A

AS – Carrier with one normal gene A and one abnormal S gene

SA – Carrier with one normal gene A and one abnormal S gene

SS – SCA-affected progeny with two copies of abnormal S gene

The chance of getting Sickle Cell Anemia depends on the pattern of inheritance and the genotypes of the parents as described above.

If Both parents have sickle cell trait - i.e. each has one normal hemoglobin gene and one sickle cell gene, the child has-

50% chance of inheriting sickle cell trait (one normal gene, one sickle cell gene),

25% chance of inheriting sickle cell disease (two sickle cell genes)

25% chance of not inheriting either the trait or the disease (two normal genes).

If one parent has sickle cell trait i.e. one normal gene and one sickle cell gene and the other parent is normal i.e. has no such genes, the risks are as follows-

50% chance of inheriting sickle cell trait.

50% Chance of being normal i.e. two normal genes with no risk of inheriting sickle cell disease or trait.

If one parent has sickle cell disease i.e. two sickle cell genes and the other parent has sickle cell trait i.e. one normal gene and one sickle cell gene, the child’s risks are as follows-

50% chance of inheriting sickle cell trait.

50% chance of inheriting sickle cell disease.

If one parent has sickle cell disease and the other parent has two normal hemoglobin genes, the risks are as follows-

100% chance of inheriting sickle cell trait,

No chance of inheriting the disease

If both parents have sickle cell disease-

100% chance of inheriting the disease.