Neutropenia

The most common cause of neutropenia is decreased production in the bone marrow, which can be caused by hereditary disorders, cancer, certain medications, radiation, and B₁₂ or folate deficiency. It may be an acute or a long-standing condition.

Neutropenia can also be caused by increased destruction of white blood cells. This can occur in severe infection and in some autoimmune disorders.

A third type of neutropenia is caused by sequestration and margination of white blood cells. This is seen in hemodialysis.

Cyclical neutropenia is when the number of neutrophils in the blood vary over time in a cyclical manner. The period is generally from 3-4 weeks, and is unrelated to the menstrual cycle in women.

There is usually a mild neutropenia in viral infections.

Neutropenia may also just be part of a general pancytopenia[?], where all the blood's cells are low in number.