Neutrophil granulocytes are the most abundant form of white blood cells, constituting 50-70% of the circulating WBCs, which play a vital role in the immune system by phagocytosis of foreign molecules and the release of cytotoxic molecules by degranulation. Neutropenia is a condition characterized by an abnormally low level of neutrophils in the circulating blood. Various classes of neutropenia are recognized. The Nonimmune Chronic Idiopathic Neutropenia of Adults (NI-CINA) is a mild form of neutropenia, in which for some unexplained reason, the number of circulating neutrophils persistently remains below the accepted reference range (2.5 x 10power9 to 7.5 x 10power9 neutrophils per Litre). This reference range tends to change with the population considered, since lower counts of neutrophils are considered normal for some ethnic groups like Africans and Arabs. There is no evidence for an underlying autoimmune disease, nutritional deficiency, or myelodysplasia, although the bone marrow analysis may reveal varied results, ranging from a hyperplastic to a hypoplastic myeloid series. The condition is clinically quite benign, with a large number of affected cases being discovered accidentally during examination of routine laboratory tests.

NI-CINA differs from the neonatal form of neutropenia by the age of appearance of the condition, its higher incidence in the females, a reduced tendency to go into spontaneous remission, and its association with anemia and thrombocytopenia.

Many suggestions have been made to explain the underlying pathology and molecular genetics of NI-CINA. Some studies point to the existence of an unrecognized low-grade chronic inflammatory process, resulting in the decreased production of neutrophils in the bone marrow, as well as an increase in their margination as well as extravasation in the periphery. Polymorphisms in HLA phenotypes have been linked to the development of NI-CINA, especially the HLA-DRB1*1302 haplotype. In addition, at least two patients with NI-CINA were found to harbor heterozygous mutations in the GFI-1 (Growth Factor-Independent 1) gene, which has also been implicated in the severe form of neutropenia.