Thalassemia is an inherited blood disorder that occurs when the body does not make enough or makes an abnormal form of hemoglobin, an important component of red blood cells. With a lack of hemoglobin, the red blood cells are unable to function properly, meaning that there is not enough oxygen delivered to cells in the body, causing people to feel tired, weak, or short of breath (anemia). Severe anemia can lead to damage to the organs and death. There are two main types of thalassemia: alpha thalassemia and beta thalassemia. Both alpha and beta include two forms: thalassemia major and thalassemia minor. Thalassemia occurs most commonly in persons from Southeast Asia, the Mediterranean, and in those of African descent. The most severe form of alpha thalassemia major causes stillbirth. Children who are born with thalassemia major, also known as Cooley’s anemia, are normal at birth but develop severe anemia during the first year of life, and can also develop other symptoms including bone deformities in the face, fatigue, growth failure, shortness of breath, and yellow skin.