The normal white blood cell count is (4-10) x 10^9/L. The main component of white blood cells is neutrophils, which account for 50%-70% of the total. What diseases can be caused by hypocellularity? First, it is easy to suffer from infectious diseases. Leukocytes quickly swallow foreign substances and produce antibodies that effectively defend against pathogens and play an important role in immunity to disease. If the body’s white blood cells are too low, it is prone to various infectious diseases, even fatal infectious diseases. Second, the immune system is reduced. Low white blood cells are responsible for the body’s immunity, and a low white blood cell count can reduce the body’s immunity. A mild decrease is called granulocytopenia, and a severe deficiency is called granulocyte deficiency, which is dangerous and can cause serious infections leading to death. Thirdly, the body will experience uncomfortable symptoms. Low leukocytes generally cause non-specific symptoms such as dizziness, fatigue, limb weakness, loss of appetite, low fever, and insomnia. A small number of patients can also be asymptomatic, while some patients have recurrent mouth ulcers, lung infections, or urinary tract infections. In leukopenia leading to granulocyte deficiency, the onset of the disease is often acute, with high fever, chills, headache, fatigue, or extreme weakness. Sometimes necrotic ulcers may develop in the mucous membranes of the nose, mouth, skin, rectum, anus, and vagina, and these uncomfortable symptoms can seriously affect the patient’s work and life.