About Immune Thrombocytopenic Purpura (ITP)

There are a number of diseases known as autoimmune diseases, in which the body's own immune system attacks an otherwise healthy part of the body. One of these autoimmune diseases is ITP, which stands for immune thrombocytopenic purpura, and is also known as idiopathic (id-ee-oh-path-ick) thrombocytopenic purpura. (Idiopathic is used to describe a disease when the underlying cause is unknown.)¹ In ITP, the immune system makes antibodies against the body's platelets and platelet producing cells called megakaryocytes. Platelets are small cells in the blood that are needed for your blood to clot. This autoimmune process is believed to happen in two ways²:

1. The platelets are treated as foreign cells, coated with antibodies, and destroyed by the spleen.²
2. The immune system may also damage the cells that make new platelets. This decreases the number of platelets that are produced.^3,4

ITP is a type of disease that results in thrombocytopenia (throm-bo-sigh-toe-peen-knee-a), which means having a low platelet count. A typical platelet count in a healthy person is between 150,000 and 450,000 per microliter of blood; this can also be expressed as 150 to 450 x 10⁹/liter.⁵

There are several types of thrombocytopenia. ITP is different from many other types of thrombocytopenia because patients with ITP often have lower than expected levels of a protein called thrombopoietin (throm-bo-po-eat-in) (TPO). The body makes TPO, a chemical that stimulates the production of platelets.

ITP can be either acute or chronic. Acute ITP, which is most commonly diagnosed in young children, starts suddenly and often goes away after a few weeks or months. Chronic ITP is more common in adults and often does not go away by itself.⁶