Idiopathic thrombocytopenic purpura or immune thrombocytopenic purpura is an autoimmune disease. These are a class of diseases where the body considers a normal part of itself foreign (in this case platelets), and it attacks the "foreign cells". In ITP, the platelets are "coated" by antibodies and the spleen recognizes this as something to be removed from circulation. As a result, these platelets are trapped in the spleen until they die and are recycled. The problem is that the body keeps making the antibody so a replacement generation of platelets also gets coated, and the cycle continues.

Thrombocytopenia means low platelets, and purpura refers to the purple looking spots and bruises that appear under the skin and mucous membranes (petechiae and ecchymoses). So, ITP is a bruising that is caused by low platelets which are the result of an immune dysfunction.

Some cases of ITP are caused by drugs and others are associated with infection, pregnancy, or immune disorders. About half of all cases are classified as "idiopathic" meaning the cause is unknown. Approximately 2-4% of CLL patients develop ITP. It can occur at any stage of CLL.

The main symptom of ITP is bleeding which can include bruising and tiny red dots on the skin or mucous membranes. In some instances bleeding from the nose, gums, digestive or urinary tracts may also occur. ITP is often accompanied by fatigue and sometimes by depression.

ITP is characterized more by its description than the specific properties of the disease. It is the diagnosis when platelets are abnormally low and other diseases that can cause low platelets have been ruled out. The diagnosis of ITP is supported when a complete blood count and bone marrow biopsy or aspirate finds normal or increased platelet forming cells (megakaryocytes).

Treatment is based on symptoms. In some cases no treatment is needed. In most cases, corticosteroids, such as prednisone, are the first line of treatment because corticosteroids prevent antibody formation. Intravenous infusions of immunoglobulin (IVIg) may be used as the next line of treatment. Splenectomy is successful in about 75% of patients who have not responded to other therapy. While it may seem overly aggressive to remove the spleen, many people think that it is the spleen that is actually causing the problem through over zealous removal of the platelets. These platelets can and do work just as well as uncoated platelets, so removing the spleen allows them to live a "normal" lifespan and work as they should. Other drugs used with refractory ITP include cyclosporine, vincristine, danazol, and azathioprine (imuran).