The common causes of leukopenia and agranulocytosis are: (1) Drug factors: There are many drugs that can cause leukopenia, mainly including anticancer drugs, chloramphenicol, sulfonamides, anti-inflammatory painkillers, drugs for treating hyperthyroidism and drugs for treating diabetes. (2) Infection factors: Many infectious diseases can cause cytopenia, such as injury, virus infection, mycoplasma pneumonia, infectious pneumonia, miliary tuberculosis and so on. (3) Hematological diseases: such as acute leukemia, malignant lymphoma, malignant histiocytosis, hypersplenism, aplastic anemia, etc. (4) Exposure to radiation: such as exposure to X-rays, cobalt 60 and phosphorus 32. (5) Others: connective tissue disease, systemic lupus erythematosus, liver cirrhosis, especially splenomegaly.

White blood cells are the frontline guards of inflammatory reaction, gathering and swimming to the inflammatory site for phagocytosis. The biggest harm is decreased immunity and easy infection.