A defect anywhere in the neutrophil life cycle can lead to dysfunction and compromised host defenses. In-flammation is often depressed, and the clinical result is often recurrent and severe bacterial and fungal infections. Aphthous ulcers of mucous membranes, gingivitis, and periodontal disease are common. The most common neutropenias are iatrogenic, resulting from the widespread use of cytotoxic or immunosuppressive therapies.