Fludarabine is a chemotherapeutic drug and a purine analogue that is used clinically mainly in B-cell chronic lymphocytic leukemia, and patients with chronic lymphocytic leukemia receive at least one course of treatment with alkylating agents, and fludarabine therapy is generally required when the disease is ineffective or progresses. The usual dose of fludarabine is 25-30 mg per square meter administered intravenously once daily for 5 days. Clinically, patients with chronic gonorrhea usually experience significant myelosuppressive effects after fludarabine application, with a decrease in peripheral blood leukocytes, red blood cells and platelets, and patients are prone to fever, including pneumonia and perianal infection, etc. Therefore, it is necessary to review the blood routine in a timely manner after fludarabine application. If the peripheral blood system is significantly decreased, the patient needs to strengthen the supportive treatment, including the application of recombinant human granulocyte colony-stimulating factor and platelet transfusion therapy, etc.