<unk>  is a disease in which the body fails to produce blood cells in sufficient numbers. Blood cells are produced in the bone marrow by stem cells that reside there.<unk>  causes a deficiency of all blood cell types: red blood cells, white blood cells, and platelets. It occurs most frequently in people in their teens and twenties but is also common among the elderly. It can be caused by heredity, immune disease, or exposure to chemicals, drugs, or radiation. However, in about half of cases, the cause is unknown.<unk>  can be definitively diagnosed by bone marrow biopsy. Normal bone marrow has 30–70% blood stem cells, but in<unk> , these cells are mostly gone and are replaced by fat. First-line treatment for<unk>  consists of immunosuppressive drugs—typically either anti-lymphocyte globulin or anti-thymocyte globulin—combined with corticosteroids, chemotherapy, and ciclosporin. Hematopoietic stem cell transplantation is also used, especially for patients under 30 years of age with a related, matched marrow donor.<unk>  is known to have caused the deaths of Eleanor Roosevelt and Marie Curie.
Aplastic anemia
Acute lymphoblastic leukemia
Refractory anemia with excess of blasts
Polycythemia vera
Myelodysplastic syndrome
Myomatous erythrocytosis syndrome
Essential thrombocythemia
Refractory cytopenia of childhood