The perennial platelet (40~50)×10^9/L may be caused by drugs and physical factors, or may be related to immune factors, infectious factors, etc., and should consult the doctor in time to find out the cause of the disease. 1. Drugs and physical factors: patients who receive radiotherapy and chemotherapy all year round and use some chemotherapy drugs, such as methotrexate, may cause bone marrow hematopoietic inhibition leading to thrombocytopenia, with perennial platelets (40~50)×10^9/L. In addition, long-term exposure to phenol, formaldehyde and other chemicals may cause thrombocytopenia. In addition, long-term exposure to phenol, formaldehyde and other chemical substances can also cause thrombocytopenia. 2. Immune factors: mainly caused by autoimmune reaction leading to platelet destruction or excessive consumption, etc. Common diseases include idiopathic thrombocytopenic purpura, systemic lupus erythematosus, etc. Patients may suffer from anemia, bleeding, etc., which may lead to corresponding reduction of platelets and red blood cells. 3. Infectious factors: common diseases such as sepsis, septicemia, etc., due to the invasion of pathogenic microorganisms and their toxic products into the blood, resulting in stagnation of bone marrow hematopoiesis, which causes a decrease in platelets, and in severe cases, spontaneous bleeding. In addition, syphilis, chronic hepatitis B and other patients, due to infection, the body through the immune mechanism, produce anti-platelet antibodies, may also appear thrombocytopenia. 4. Blood diseases: such as aplastic anemia, acute leukemia, etc., thrombocytopenia can also occur. Perennial platelet (40~50)×10^9/L, should consult the doctor in time, improve the relevant examination, if necessary, bone marrow aspiration examination, in order to clarify the diagnosis, and under the guidance of the physician to carry out targeted treatment.