The number of peripheral blood leukocytes is called leukopenia when it is consistently lower than 3.5×109/L. Diseases that can lead to leukopenia are broadly classified into the following three categories according to the etiology and pathogenesis: a. Leukopenia Leukocytes are a type of human blood cell, and certain diseases that affect human hematopoietic stem cells, such as aplastic anemia, myelodysplastic syndrome, myeloma and other diseases can affect leukocyte generation and maturation, resulting in a decrease in white blood cells. In addition, when the body is exposed to chemical toxins, ionizing radiation and certain drugs, the hematopoietic environment can also be damaged, thereby inhibiting leukocyte production. Second, excessive destruction or consumption of leukocytes When the body suffers from certain viral infections or sepsis, the number of leukocytes decreases due to excessive consumption at the site of inflammation. In addition, autoimmune system diseases such as hypersplenism, hepatitis or systemic lupus erythematosus can also destroy leukocytes in the body, resulting in a decrease in leukocytes. In normal circumstances, leukocytes are evenly distributed in the venous blood, but when the patient has endotoxemia or dialysis, the leukocytes will accumulate in the pulmonary vessels, spleen, etc. Although the total number of leukocytes in the body is normal, the number of leukocytes in our blood tests will be lower than normal, so it is called pseudogranulocytosis. hypoplasia. When a blood test indicates that the white blood cell count is consistently lower than normal, it is important to seek prompt medical attention to improve the systemic and formal examination and laboratory tests to clarify the diagnosis and then provide targeted treatment.