Adapted from NEUTROPENIA, Causes, Consequences, and Care, Provided by The Neutropenia Association Inc.1993
Neutropenia occurs when blood neutrophil counts are below 1500 per microliter. Some people are born with it like patients with SDS. It can happen after a viral infection. In some cases the cause can be a side effect of a drug, or exposure to certain poisons. People can get neutropenia when treated for cancer with chemotherapy drugs. Sometimes it happens for no known reason.

Blood is made up of billions of cells. There are many different types of blood cells, but most of the time you hear about two kinds - red cells and white cells. There are more red cells than any other type of blood cell. They are very important as they carry oxygen from your lungs to all parts of your body. White blood cells are just as important, but for a very different reason. One of their jobs is to protect you from infection. There are several kinds of white cells. Each has a special function. The most common ones are:

	Neutrophils which surround and destroy bacteria in your body; these include polys and bands. They are the most numerous of the white blood cells. They make up about 56 percent of white blood cells.
	Lymphocytes which are the key part of your body’s immune system, and defend against viruses.
	Basophils These are indicators of allergic reactions to a variety of factors.
	Eosinophils These will rise above the normal range with allergic reactions and parasitic infections.
	Monocytes These cells will destroy the germ cells that have killed off by all of the other types of white cells.

The term neutropenia describes the situation where the number of neutrophils in the blood is too low. Neutrophils are very important in defending the body against bacterial infections, and therefore, a patient with too few neutrophils is more susceptible to bacterial infections. It is determined by calculating the Absolute Neutrophil Count.

Everyone has been sick with an infection at one time or another. That’s because it’s easy for bacteria and viruses that cause infections to get inside the body. Healthy people don’t often get infections even though bacteria and viruses are all around us, even in the air we breathe.
The body protects itself against the constant risk of infection by making a lot of neutrophils. They are your main defense against infections.

People with neutropenia get infections easily and often. Most of the infections occur in the lungs, mouth and throat, sinuses and skin. Painful mouth ulcers, gum infections, ear infections and periodontal disease are common. Severe, life-threatening infections may occur. Often the child or adult must be hospitalized and receive intravenous antibiotics. Your doctor uses blood tests to find out whether you have enough neutrophils.

The level of neutropenia may vary considerably. In general, the blood of healthy adults contains about 1500 to 7000 neutrophils per mm3 (1.5 - 7.0 x 109 /1). In children under 6 years of age the neutrophil count may be lower. The severity of neutropenia generally depends on the absolute neutrophil count (ANC) and is described as follows:

	Mild neutropenia, when the ANC falls below a lower limit of 1500 per mm3 (1.5 x 109 /1), but remains higher than 1000 per mm3 (1.0 x 109 /1).
	Moderate neutropenia, when the ANC falls between 500 per mm3 and 1000 per mm3 (0.5 x 109 /1 - 1.0 x 109 /1)
	Severe neutropenia, when the ANC falls below 500 per mm3 (0.5 x 109 /1)