Essential thrombocytopenia is a rare blood disease characterized by reduced levels of platelets in the circulating blood. Platelets are essential to blood-clotting and, if they are in short supply, bleeding may occur that can become life-threatening. The platelets are produced in the bone marrow and may be in reduced supply because of (1) impaired or reduced platelet production in the marrow, (2) increased destruction of platelets faster than they can be replaced by the marrow, or (3) the presence of one of several genetic disorders. There are also false thrombocytopenias. Major symptoms include a tendency to bleed excessively into the skin or mucous membranes, especially during menstruation, nosebleeds and bleeding gums.