Aplastic anemia: Anemia due to failure of the bone marrow to produce blood cells, including red and white blood cells as well as platelets. Aplastic anemia frequently occurs without a known cause. Known causes include exposure to chemicals (benzene, toluene in glues, insecticides, solvents), drugs (chemotherapy, gold, seizure medications, antibiotics, and others), viruses (HIV, Epstein-Barr), radiation, immune conditions (systemic lupus erythematosus, rheumatoid arthritis), pregnancy, paroxysmal nocturnal hemoglobinuria, and inherited disorders (Fanconi's anemia).

Symptoms of aplastic anemia include fatigue, bruising, bleeding, shortness of breath, fever, chills, and less frequently, bone pain. The diagnosis is based on the presence of low red and white blood cell and platelet counts and a decrease in the normal cells of the bone marrow.

Treatment depends on the suspected cause of the condition. All medications which might suppress the bone marrow are discontinued. Male hormone (androgens) may be given to stimulate the suppressed bone marrow to become more active. Bone marrow stimulating factors may be given intravenously. Blood transfusions are often required. Precautions to avoid infections are taken when the white blood cell counts are severely lowered. Bone marrow transplantation may be considered. Suppression of the immune system may be indicated. Immunosuppression therapy can include antithymocyte globulin, cortisone medications, and cyclosporine. Treatment with antithymocyte globulin has been successful for some patients and permitted them to make sufficient blood cells to stay transfusion-free for 5 years or more.