Idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder that occurs when the immune system mistakenly attacks and destroys platelets, which are necessary for blood clotting. Symptoms may include easy bruising, petechiae (small purple or red dots on the skin), and prolonged bleeding from cuts. Treatment may involve medications to suppress the immune system or increase platelet production, as well as blood transfusions in severe cases.