Aplastic anemia is a disease in which the bone marrow does not make enough blood cells for the body. The 3 types of blood cells your body needs are: red blood cells (to carry oxygen), white blood cells (to fight infection), and platelets (to control bleeding). When all 3 types of blood cells are very low in number, the person has severe aplastic anemia (SAA).
Aplastic anemia is rare. In the United States, about 600-900 people are diagnosed each year, according to the Aplastic Anemia and MDS International Foundation. Aplastic anemia occurs more frequently in eastern Asian countries. It can affect people of any age, but it is most common in young adults. For most cases, the cause is unknown. There are some rare inherited diseases, such as Fanconi anemia, where SAA can develop over time in some patients.