Sickle cell anemia, also known as sickle cell disease or SCD, is a genetic disorder that causes the body to produce an abnormal variant of hemoglobin called hemoglobin S. This version of the iron-containing protein that carries oxygen to the lungs is incorrectly-shaped, producing cells that won't flow smoothly through the blood vessels and easily collect in small veins. Sickled hemoglobin cells are much shorter-lived than ordinary round blood cells, resulting in an increasing level of anemia, since the sufferer's body cannot keep up with the rate of cell death.

People with sickle cell anemia often suffer long episodes of pain associated with the obstruction of small blood vessels, as well as dizziness, shortness of breath, fatigue and other symptoms of anemia. They may develop lung infections and a breathing problem called acute chest syndrome, with chest pain, fever and coughing. Sufferers are at a high risk of stroke, especially if they are children. This problem occurs most often in people of African and Mediterranean descent, including some from Central and South America with European ancestry. 

Testing for sickle cell anemia often involves a hemoglobin solubility test, which measures the presence of abnormal hemoglobin, as well as the amount of these sickle cells in the blood. This test may be accompanied by hemoglobinopathy, complete blood count, blood smear and iron study tests, as well as DNA analysis. After sickle cell anemia has been diagnosed, patients may receive long-term penicillin therapy, hydroxyurea or occasional blood transfusions to prevent more serious problems later on.