Immune Thrombocytopenic Purpura (ITP)

What Is It?

Immune thrombocytopenic purpura (ITP), also known by the shorter name Immune Thrombocytopenia (same abbreviation ITP), can be understood by looking at the three terms that make up its name:

  • Immune indicates that the illness is caused by the immune system, which makes cells and antibodies that attack the person's own platelets — the parts of the blood that help the blood to clot.

  • Thrombocytopenic means that the illness is related to low levels of thrombocytes, another name for platelets. Platelets are produced in the bone marrow (the central lining of the bones). The body needs adequate numbers of functioning platelets to allow blood to clot and to limit bleeding if you are cut or experience other types of trauma.

  • Purpura means that the illness produces a red or purple rash that is caused by bleeding under the skin. This is only one manifestation of the disease

In short, ITP is an illness in which unusually low levels of platelets lead to purpura and other forms of abnormal bleeding.

In people with ITP, the immune system produces abnormal proteins called antiplatelet antibodies. These misdirected proteins attach themselves to the surface of blood platelets as if the platelets were "foreign" or invading bacteria or viruses. As the affected platelets circulate in the bloodstream, they are recognized as abnormal by the spleen and removed from the blood.

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