Definition of Idiopathic aplastic anemia:

Idiopathic aplastic anemia is a condition in which the bone marrow fails to properly make blood cells. Bone marrow is the soft, fatty tissue in the center of bones.

See also:

• Anemia
• Secondary (acquired) aplastic anemia

Causes, incidence, and risk factors:

Aplastic anemia results from injury to the blood stem cells, immature cells in the bone marrow that give rise to all of other blood cells types. The injury causes a decrease in the number of every type of blood cell in the body -- red cells, white cells, and platelets. Low numbers of red cells, white cells, and platelets is a condition called pancytopenia.

Idiopathic means the cause is unknown. However, idiopathic aplastic anemia is thought to occur when the body's immune system mistakenly destroys healthy cells. This is called an autoimmune disorder.

The disease may be acute or chronic, and may get worse over time. There are no known risk factors.

Aplastic anemia may also be caused by certain medical conditions (such as pregnancy or lupus) or exposure to some toxins or drugs (including chemotherapy). See: Secondary (acquired) aplastic anemia

In some cases, aplastic anemia is associated with another blood disorder called paroxysmal nocturnal hemoglobinuria (PNH).