Selected white cell disorders.

The emergency physician frequently is confronted with an abnormal white blood cell count when evaluating patients. Leukocytosis may be caused by malignancy, infection, or a variety of other reasons. Leukopenia is an increasingly common finding as the population of immunocompromised patients continues to expand. This article reviews the differential diagnosis of leukocytosis and leukopenia. The management of the neutropenic patient with and without fever is also reviewed and includes currently recommended empiric antibiotic regimens.