Clinical meaning
Febrile neutropenia is a medical emergency defined as a single oral temperature of 38.3 C (101.0 F) or higher, or a sustained temperature of 38.0 C (100.4 F) or higher for one hour, in a patient with an absolute neutrophil count (ANC) below 500 cells per microliter, or an ANC below 1000 cells per microliter with an expected decline to below 500 within 48 hours. Neutrophils are the most abundant type of white blood cell and serve as the first line of cellular defense against bacterial and fungal infections. They are produced in the bone marrow from myeloid stem cells through a process called granulopoiesis, which takes approximately 7-14 days from stem cell to mature neutrophil release into the bloodstream. Circulating neutrophils have a very short lifespan of approximately 6-12 hours in the blood before migrating into tissues. When pathogens breach the body's physical barriers (skin, mucous membranes), tissue macrophages and damaged cells release chemotactic factors (interleukins, complement fragments, bacterial products) that attract neutrophils to the site of infection through a process called chemotaxis. Neutrophils kill pathogens through phagocytosis (engulfing...