What are the causes of leukopenia?

The main causes of leukopenia (reduced white blood cell count) include the following aspects: 1. **Impaired production of white blood cells**: This may occur due to decreased proliferation of hematopoietic stem cells, aplastic anemia, or other conditions caused by chemical toxins, radiation exposure, or abnormal cell infiltration into the bone marrow. 2. **Increased destruction of white blood cells**: In pathological conditions such as bacterial, fungal, viral, or rickettsial infections and allergic reactions, the bone marrow may produce increased numbers of granulocytes. However, transient leukopenia may occur during severe infections. 3. **Abnormal distribution of white blood cells in circulating blood**: Under pathological conditions such as malaria or anaphylactic shock, the number of white blood cells in the marginated pool increases, while the number of neutrophils in the circulating pool decreases. 4. **Other factors**: Deficiencies in vitamin B12 or folic acid, as well as connective tissue diseases such as systemic lupus erythematosus (SLE), may also cause leukopenia. Leukopenia has multiple potential causes, and diagnosis and treatment should be based on the patient's specific clinical presentation.