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By Mayo Clinic staffNeutropenia (noo-tro-PE-ne-uh) is an abnormally low count of neutrophils, white blood cells that protect your body from bacteria and fungi. You have several types of white blood cells, and between 45 and 70 percent of all white blood cells are neutrophils.
The threshold for defining neutropenia varies slightly from one medical practice to another. Neutropenia in adults is generally defined as a count of 1,700 or fewer neutrophils per microliter of blood. The cell count indicating neutropenia in children varies with age.
The lower your neutrophil count, the more vulnerable you are to infectious diseases. If you have severe neutropenia — fewer than about 500 cells per microliter of blood — bacteria normally present in your mouth and digestive tract can cause infections.