Platelets are anuclear blood cells whose function is to form blood clots when we injure ourselves, to prevent excessive blood loss. Thrombocytopenia is a relative low number of platelets in the blood. Thrombocytopenia has several possible causes, including the trapping of platelets in spleen, reduced production of platelets and increased breakdown of platelets. Some examples of an increase in platelet breakdown include pregnancy, idiopathic thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome, infection, autoimmune diseases and medications (e.g., heparin). Thrombocytopenia may often be asymptomatic and can only be revealed by full blood cell count. Alternatively, it may cause excessive bruises and/or bleeding. In some cases, platelet count is so low that dangerous internal bleeding occurs.