Low leukocytes and low neutrophils can be seen in an overall deficiency in production, which can be classified as reduced production versus impaired maturation. Ionizing radiation and chemical toxins can lead to reduced production, as can hematopoietic stem cell disorders such as aplastic anemia. Regarding maturation disorders, it is mainly the deficiency of folic acid and vitamin B12 at the time of neutrophil maturation that leads to the inability to differentiate and mature, resulting in ineffective hematopoiesis. In addition, there is destruction or excessive depletion. Immune factors, such as drug-related or related to autoimmune diseases, they can lead to excessive destruction of leukocytes, and non-immune factors can also lead, such as an enlarged spleen accompanied by hypersplenism, where granulocytes can remain in the body and destroy too much, leading to a decrease.