What type of cell is a sickle cell?

A misshapen red blood cell (RBC). Sickle cell-shaped RBCs occur in genetically predisposed people. It is an autosomal genetic blood disorder that causes a mutation in the hemoglobin gene which results in these inflexible and sticky crescent shaped cells. Because of their shape, that is so different from a normal doughnut-shaped RBC, and their sticky, rigid characteristics, they can get stuck and clogged and obstruct blood flow with resulting vessel and circulatory problems, pain, and shortened life span.

According to the US National Institute of Health's National Heart, Lung and Blood Institute:

Sickle cell anemia is most common in people whose families come from Africa, South or Central America (especially Panama), Caribbean islands, Mediterranean countries (such as Turkey, Greece, and Italy), India, and Saudi Arabia.

In the United States, it's estimated that sickle cell anemia affects 70,000-100,000 people, mainly African Americans. The disease occurs in about 1 out of every 500 African American births. Sickle cell anemia also affects Hispanic Americans. The disease occurs in more than 1 out of every 36,000 Hispanic American births.

More than 2 million Americans have sickle cell trait. The condition occurs in about 1 in 12 African Americans.

Some studies have suggested that this genetic mutation is most prevalent in people with ancestry from the climates that commonly have malaria. It is hypothesized that this trait has beneficial effects and/or symptom ameliorating effects for malaria victims and has evolved in those groups as a mutation of the cells to assist in overcoming that parasitic disease.