Sickle Cell Disease Overview

Sickle cell disease is a blood disorder caused by a genetic mutation. The disease occurs more often in people that come from parts of the world where malaria is or was common.

An estimated 100,000 Americans have sickle cell disease (SCD). According to the Centers for Disease Control (CDC) and the National Heart, Lung, and Blood Disease Institute (NHLBI), the disease occurs more often in people of African, African-Caribbean, Mediterranean, Middle Eastern, Asian, and Indian descent who come from parts of the world where malaria is or was common. The theory is that people who carry the sickle cell trait are less likely to have severe forms of malaria. While the sickle cell trait may confer some protection, for those with SCD, malaria can be very serious and life-threatening.

Sickle cell anemia (SCA) is the most common and most severe form of sickle cell disease (SCD), a group of inherited blood disorders caused by a genetic mutation. This mutation affects the body’s production of hemoglobin, the oxygen-carrying protein in red blood cells. The defective hemoglobin causes some red blood cells to change from healthy, flexible donut-shaped cells that move easily through the bloodstream into misshapen sickle-shaped versions. And because the sickled cells are rigid and sticky, they tend to clump together creating micro-clots that block or restrict blood and oxygen flow in small blood vessels (microvasculature).

These blockages can occur just about anywhere in the body triggering a sickle cell crisis, an episode of severe and sometimes excruciating pain that can last for hours, days, or longer. When a severe crisis occurs it usually means a trip to the emergency room or a hospital stay for pain management and close monitoring for other complications. And over time, sickle cell disease can permanently damage vital organs, including the heart, lungs, kidneys, spleen, and joints. 

Sickle cells and regular blood cells Sickle cells are stiff and C-shaped. Blood and oxygen flow gets blocked by sickle cells, which don't live as long as regular blood cells and cause anemia. (Source: 123RF)


In the United States (and many other countries) all newborns are screened for SCD. A negative test result means there is no sickle cell gene present. A positive blood test reveals the presence of the gene. However, a subsequent test is needed to determine if the child has inherited one or two defective genes. People who have SCD inherited a defective gene from each parent.

Those who inherit only one defective gene are considered carriers. They have the sickle cell trait (SCT) but are generally healthy and don’t show any signs or symptoms of SCD. SCD occurs in about 1 out of every 365 Black or African-American births and roughly 1 out of every 16,300 Hispanic-American births. About 1 in 13 African-American babies is born with SCT, which means that they have inherited only one defective gene.

Updated on: 04/29/19
Continue Reading:
Symptoms and Complications of Sickle Cell Disease