Immune thrombocytopenia is a disorder characterized by a blood abnormality called thrombocytopenia, which is a shortage of blood cells called platelets that are needed for normal blood clotting. Affected individuals can develop red or purple spots on the skin caused by bleeding just under the skin's surface. Immune thrombocytopenia usually happens when your immune system mistakenly attacks and destroys platelets, which are cell fragments that help blood clot. In adults, this may be triggered by infection with HIV, hepatitis or H. pylori the type of bacteria that causes stomach ulcers. Symptoms may include easy bruising, bleeding and pinpoint-sized reddish-purple spots on the lower legs. Adults commonly need treatment with medication for bleeding. Rarely the spleen may need to be removed.