(1) Decreased white blood cell production: including bone marrow hematopoietic function inhibition or pathological hematopoiesis, infiltration of various malignant tumor cells into bone marrow, nutritional deficiency, blood cell maturation disorder, etc. (2) Excessive destruction of white blood cells: including destruction caused by various drugs and autoimmune diseases; (3) Abnormal white blood cell distribution: also known as pseudoleukopenia, in fact, the number of white blood cells in the body is not reduced, but transferred to the spleen or adsorbed on the blood vessel wall of the whole body (which can be confirmed by adrenaline test), and can be increased when necessary.
Generally speaking, in addition to various blood diseases, various infections (especially viral infections) and various drugs can often cause leukopenia, especially drug abuse, which is often an important cause of leukopenia.