Sickle cell trait

Overview
Sickle cell trait describes the way a person can inherit some of the genes of sickle cell disease, but not develop symptoms. Sickle cell disease is a blood disorder in which the body produces an abnormal type of the oxygen-carrying substance hemoglobin in the red blood cells.

Normal hemoglobin is called hemoglobin A, but people with sickle cell disease have only hemoglobin S, which turns normal, round red blood cells into abnormally curved (sickle) shapes.

Normally, a person inherits two genes (one from each parent) that produce beta-globin, a protein needed to produce normal hemoglobin (hemoglobin A). A person with sickle cell trait inherits one normal beta-globin gene (hemoglobin A) and one defective gene (hemoglobin S).

People with sickle cell trait rarely have symptoms due to the condition because they also have some normal hemoglobin. However, they can pass the sickle cell trait to their children, and in rare cases, exercise-induced dehydration or exhaustion can cause healthy red blood cells to turn sickle-shaped, which can cause death.

A person in whom both beta-globin genes are abnormal (they produce hemoglobin S) has sickle cell disease, which can cause serious problems. Both parents must have either the sickle cell trait or the disease itself for a child to have sickle cell disease.

People who have the sickle cell trait have reduced susceptibility to malaria, due to natural selection for the heterozygote advantage. However, people with the sickle cell trait can still contract severe cases of malaria.