The absence of platelets refers to a serious reduction in the number of platelets in the body. In clinical practice, the common diseases that cause a serious reduction in platelets are: i. Immune thrombocytopenia, which is an autoimmune disease that causes excessive destruction of platelets in the peripheral blood due to the production of antibodies against one’s own platelets and is accompanied by impaired maturation of megakaryocytes. Sometimes the number of platelets in the peripheral blood is very low, sometimes even zero. Patients may also show signs of bleeding, such as bleeding spots on the skin, petechiae, nasal and gum bleeding, and internal bleeding. In addition to platelet reduction, patients with heavy aplastic anemia also have severe anemia, infection and a series of other symptoms. Third, leukemia patients after chemotherapy, the patient into the myelosuppression phase will also appear serious reduction of platelets.