Sickle cell anemia (HbSS) is a genetic blood disorder that is the most common, severe type of sickle cell disease, in which the red blood cells, instead of being flexible and round, are rigid, sticky, and shaped like sickles or crescent moons (C-shaped). This rigidity and stickiness of red blood cells makes the hemoglobin in the cells carry less oxygen and get stuck in small blood vessels, while slowing or blocking blood and oxygen to the body tissues. Sickle cells additionally die early, causing a chronic shortage of red blood cells. When sickle cells get stuck in small blood vessels, they can cause pain, infection, acute chest syndrome, and stroke.
In the United States, sickle cell anemia occurs most frequently in African Americans and Hispanic Americans.