Neutropenia or neutropaenia, is an abnormally low concentration of neutrophils (a type of white blood cell) in the blood.[

Neutrophils make up the majority of circulating white blood cells and serve as the primary defense against infections by destroying bacteria, bacterial fragments and immunoglobulin-bound viruses in the blood.

Patients with neutropenia are more susceptible to bacterial infections and, without prompt medical attention, the condition may become life-threatening (neutropenic sepsis).

Neutropenia can be acute (temporary) or chronic (long lasting). The term is sometimes used interchangeably with “leukopenia” (“deficit in the number of white blood cells”)