The so-called leukemia is the "tumor" of the hematopoietic system, which has the nature of * * *, that is, the cells proliferate rapidly and massively, and which system proliferates rapidly is the leukemia of which system. Such as granulocytes, lymphocytes and monocytes. The proliferation of acute leukemia is obvious, but the chronic proliferation is not obvious or slightly higher.

Decrease is generally not considered leukemia.

Leukopenia is common in viral infection, tuberculosis and so on. And neutropenia.

Your terms are: 1. If your white blood cells have been low, it is physiologically low, and this situation has nothing to do; 2. Pathological decrease: mainly virus infection and neutropenia (such as chemical pollution hazards such as drugs, formaldehyde and benzene).