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

Agranulocytosis can be presented as whitish or greyish necrotic ulcer in the oral cavity, without any sign of inflammation.

Causes can be divided into these groups:[1][2][11][12] Severe bacterial infections, especially in people with underlying hematological diseases or alcoholism, can deplete neutrophil reserves and lead to neutropenia.

The congenital neutropenia (severe and cyclic type) is autosomal dominant, with mutations in the ELA2 gene (neutrophil elastase) as the most common genetic reason for this condition.

[34] Congenital neutropenia is related to alloimmunization, sepsis, maternal hypertension, twin-to-twin transfusion syndrome, and Rh hemolytic disease.

[1] Neutropenia can be the result of a variety of consequences, including taking certain types of drugs, exposure to environmental toxins, vitamin deficiencies, metabolic abnormalities, as well as cancer, viral or bacterial infections.

[36][37] Neutropenia that is developed in response to chemotherapy typically becomes evident in seven to fourteen days after treatment, this period is known as the nadir or "low point".

[38][39] Conditions that indicate the presence of neutropenic fever are implanted devices; leukemia induction; the compromise of mucosal, mucociliary and cutaneous barriers; a rapid decline in absolute neutrophil count, duration of neutropenia >7–10 days, and other illnesses that exist in the patient.

A bone marrow biopsy can identify abnormalities in myelopoesis contributing to neutropenia such as the stage of arrest in the development of myeloid progenitor cells.

[2] Bone marrow biopsies can also be used to monitor the development of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) in patients with chronic neutropenia (especially in those with severe congenital neutropenia (SCN) which carries a higher risk of MDS and AML)).

[31] Generally accepted reference range for absolute neutrophil count (ANC) in adults is 1500 to 8000 cells per microliter (μL) of blood.

Three general guidelines are used to classify the severity of neutropenia based on the ANC (expressed below in cells/μL):[42] Each of these are either derived from laboratory tests or via the formula below:

[2]Precautions to avoid opportunistic infections in those with chronic neutropenia include maintaining proper soap and water hand hygiene, good dental hygiene and avoiding highly contaminated sources that may contain a large fungal reservoirs such as mulch, construction sites and bird or other animal waste.

[47] Those who have chronic neutropenia and fail to respond to G-CSF or who have an increased risk of developing MDS or AML (due to increased dosage requirements of G-CSF or having abnormal precursor cells in the bone marrow) often require hematopoietic stem cell transplantation as a treatment.

[1] 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%.

Another Cochrane review [49] 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-CSF's.

[50] The drug was approved in February 2021 by the FDA for use in patients with extensive-stage small cell lung cancer.

[52] Neutropenia is usually detected shortly after birth, affecting 6% to 8% of all newborns in neonatal intensive care units (NICUs).

Results published demonstrated only 1% of those evaluated were neutropenic, and were commonly seen in those with HIV, viral infections, acute leukemias, and myelodysplastic syndromes.