Medical Definition of Neutrophil. Neutrophil: A type of white blood cell, a granulocyte that is filled with microscopic granules, little sacs containing enzymes that digest microorganisms. Also known as polymorphonuclear leukocyte or poly.
Definition of Neutropenia. Neutropenia: Not enough neutrophils, neutrophils being a type of white blood cell (specifically a form of granulocyte) filled with neutrally-staining granules, tiny sacs of enzymes that help the cell to kill and digest microorganisms it has engulfed by phagocytosis.
Causes of Neutropenia. Causes of Neutropenia. Most types of neutropenia are induced by drugs and chemicals (e.g. chemotherapy). Other types of neutropenia are caused by an inherited mutation in one of several genes. Severe infections can also lead to neutropenia. Sometimes there is no known cause for neutropenia.