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. Acquired neutropenia (immune-associated neutropenia) is due to anti-neutrophil antibodies that target neutrophil-specific antigens, ultimately altering neutrophil function. Furthermore, emerging research suggests neutropenia without an identifiable etiology (idiopathic neutropenia) may be the result of a  low-grade, chronic inflammatory process with an abnormal excessive production of myelosuppressive cytokines in a study conducted in the island of Crete.Neutropenia fever can complicate the treatment of cancers. Observations of children noted that fungal infections are more likely to develop in those with neutropenia. Mortality increases during cancer treatments if neutropenia is also present. Congenital neutropenia is determined by blood neutrophil counts (absolute neutrophil counts or ANC) < 0.5 × 109/L and recurrent bacterial infections beginning very early in childhood. Congenital neutropenia is related to alloimmunization, sepsis, maternal hypertension, twin-to-twin transfusion syndrome, and Rh hemolytic disease. Diagnosis
Neutropenia can be the result of a variety of consequences, including from certain types of drugs, environmental toxins, vitamin deficiencies, metabolic abnormalities, as well as cancer or infections. Neutropenia itself is a rare entity, but can be clinically common in oncology and immunocompromised individuals as a result of chemotherapy (drug-induced neutropenia). Additionally, acute neutropenia can be commonly seen from people recovering from a viral infection or in a post-viral state.
Meanwhile, several subtypes of neutropenia exist which are rarer and chronic, including acquired (idiopathic) neutropenia, cyclic neutropenia, autoimmune neutropenia, and congenital neutropenia.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. 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.Signs of infection can be subtle. Fevers are a common and early observation. Sometimes overlooked is the presence of hypothermia, which can be present in sepsis. Physical examination and accessing the history and physical examination is focused on sites of infection. Indwelling line sites, areas of skin breakdown, sinuses, nasopharynx, bronchi and lungs, alimentary tract, and skin are assessed.The diagnosis of neutropenia is done via the low neutrophil count detection on a complete blood count. Generally, other investigations are required to arrive at the right diagnosis. When the diagnosis is uncertain, or serious causes are suspected, bone marrow biopsy may be necessary. 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. 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)).