The sudden drop in white blood cells in patients with chronic granulomas is mainly due to the adverse effects of the drug. Patients with chronic granulomas usually need to use imatinib mesylate for treatment, and the use of the drug will have adverse reactions such as thrombocytopenia, edema, nausea, diarrhea and so on. Imatinib mesylate is mainly used to achieve the therapeutic purpose by inhibiting BCR-ABL protein tyrosine kinase, mediating cell behavior and blocking the proliferation and differentiation of bone marrow hematopoietic stem cells. After bone marrow suppression, there will be a decrease in red blood cells, platelets, and white blood cells, so white blood cells may suddenly fall when applying imatinib mesylate in patients with lentigo. There may be other reasons for the sudden drop of white blood cells in patients with chronic granulomas, and they should go to the hospital for examination in time to clarify the specific reasons. When using the drug treatment, you need to follow the doctor’s prescription or instructions, to avoid blindly using the drug to cause adverse consequences.