Neutropenia 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. People with neutropenia are more susceptible to bacterial infections and, without prompt medical attention, the condition may become life-threatening (neutropenic sepsis).Neutropenia can be divided into congenital and acquired, with severe congenital neutropenia (SCN) and cyclic neutropenia (CyN) being autosomal dominant and mostly caused by heterozygous mutations in the ELANE gene (neutrophil elastase). 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").Decreased production of neutrophils is associated with deficiencies of vitamin B12 and folic acid, aplastic anemia, tumors, drugs, metabolic disease, nutritional deficiency and immune mechanisms. In general, the most common oral manifestations of neutropenia include ulcer, gingivitis, and periodontitis. Agranulocytosis can be presented as whitish or greyish necrotic ulcer in oral cavity, without any sign of inflammation. Acquired agranulocytosis is much more common than the congenital form. The common causes of acquired agranulocytosis including drugs (non-steroidal anti-inflammatory drugs, antiepileptics, antithyroid and antibiotics) and viral infection. Agranulocytosis has a mortality rate of 7–10%. To manage this, the application of granulocyte colony stimulating factor (G-CSF) or granulocyte transfusion and the use of broad-spectrum antibiotics to protect against bacterial infections are recommended.
The factors promote neutrophil recovery following anticancer therapy.The administration of intravenous immunoglobulins (IVIGs) has had some success in treating neutropenias of alloimmune and autoimmune origins with a response rate of about 50%. Blood transfusions have not been effective.Patients with neutropenia caused by cancer treatment can be given antifungal drugs. A Cochrane review  found that lipid formulations of amphotericin B had fewer side effects than conventional amphotericin B, though it is not clear whether there are particular advantages over conventional amphotericin B if given under optimal circumstances. Another Cochrane review  was not able to detect a difference in effect between amphotericin B and fluconazole because available trial data analysed results in a way that disfavoured amphotericin B.
Trilaciclib, a CDK4/6 inhibitor, administered approximately thirty minutes before chemotherapy, has been shown in three clinical trials to significantly reduce the occurrence of chemotherapy-induced neutropenia and the associated need for interventions such as the administration of G-CSFs. The drug is currently under review by the FDA for use in small cell lung cancer with a decision expected by February 15, 2021. Prognosis
If left untreated, people with fever and absolute neutrophil count <500 have a mortality of up to 70% within 24 hours. The prognosis of neutropenia depends on the cause. Antibiotic agents have improved the prognosis for individuals with severe neutropenia. Neutropenic fever in individuals treated for cancer has a mortality of 4–30%. Epidemiology
Neutropenia is usually detected shortly after birth, affecting 6% to 8% of all newborns in neonatal intensive care units (NICUs).