Neutropenia can be caused when the bone marrow has a problem producing neutrophils, such as in cases of cancer, a Vitamin B12 or folic acid deficiency, in hereditary disorders like Congenital Neutropenia, exposure to pesticides, as a result of taking certain medications or undergoing radiation therapy.

It may also be caused by white blood cell destruction in other parts of the body, like in aplastic anemia, Autoimmune Neutropenia, chemotherapy and hemodialysis treatments. In some instances, a mild case of Neutropenia can occur when a person contracts a viral infection.

The measurement of how severe a Neutropenia case is will depend on a person's neutrophil count. Normal neutrophil levels in adults fall between 1,500 to 7,000 neutrophils per mm3. Children under 7 years of age may have a lower neutrophil count.

Patients with mild Neutropenia will have an absolute neutrophil count (ANC) of below 1,500 per mm3, moderate cases have an ANC of between 500 to 1,000 per mm3, while the ANC of severe Neutropenia falls below the 500 per mm3 level.

Females have a higher risk for Neutropenia, as are elderly adults. A person with severe Neutopenia will need immediate medical attention, as there is a greater potential for several types of infection to develop, such as bacterial, fungal or viral, or all three at once combined.