PTI is a blood disease caused by low platelet count - so spontaneous bleeding and bruising are quite common to patients. This is due to a deficiency in the production of these cells and mainly by a failure in the immune system, which is the barrier composed by millions of cells that guarantee the body's defense against bacteria, viruses and other microbes. He begins to recognize the platelets as foreign bodies and begins to attack them. For this reason, it is classified as an autoimmune disease.