Definition of Idiopathic aplastic anemia:

Idiopathic aplastic anemia is a failure of the bone marrow to properly make all types of blood cells.

Causes, incidence, and risk factors:

Idiopathic aplastic anemia is a condition that results from injury to the blood stem cell, a cell that gives rise to other blood cell types after it divides. As a result, there is a reduction in all blood cell types with this type of anemia. This reduction is called pancytopenia. The affected types of blood cells are red cells, white cells, and platelets.

The cause of idiopathic aplastic anemia is unknown, but is thought to be an autoimmune process (the body reacting against its own cells). Causes of other types of aplastic anemia may be chemotherapy, radiation therapy, toxins, drugs, pregnancy, inherited or congenital (present at birth) disorders, or systemic lupus erythematosus. In some cases, aplastic anemia is associated with another blood disorder, paroxysmal nocturnal hemaglobinuria (PNH).

Symptoms arise as the consequence of bone marrow failure and the loss of blood cell production. Low red cell count (anemia) leads to fatigue and weakness. Low white cell count (leukopenia) causes an increased risk of infection. Low platelet count (thrombocytopenia) results in bleeding, especially of mucus membranes and skin.

The disease may be acute or chronic, and may be progressive. Risk factors are unknown.