Congenital disorders are disorders present when a child is born; they are often life-long conditions. Kostmann syndrome or congenital neutropenia is one such condition. It causes reduced neutrophils, a type of white blood cell. Myelokathexis causes neutrophilia as well as leukopenia or reduced circulation of white blood cells. Often, if a person with one of these conditions is diagnosed with a low white blood cell count later in life, they already are aware of the cause.

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