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.
Jumean and Sudah (1983) evaluated bone marrow granulocyte reserves and the bone marrow storage pool in 10 Jordanian adult patients with chronic benign idiopathic neutropenia, by measurement of the peripheral blood granulocyte increment following the administration of hydrocortisone and lithium. The increment in each case was statistically significant, indicating retention of effective neutrophil production in stressful situations and, thus, the benignity of this disorder.
Al-Ankoodi and Rawther (2004) conducted a study to determine the percentage of healthy Omani individuals considered to be neutropenic according to both the international and Omani reference ranges, as well as the reference range that would cover 95% of the Omani population. Blood samples from 126 healthy blood donors were analyzed by Cell-Dyn 3500R automated analyzer. Only 37% of this Omani population was found to have neutrophil counts within the international reference range of 2.5 - 7.5 x 10power9/L, with 63% considered to be neutropenic. On the other hand, 64% of the subjects had neutrophil counts within the Omani reference range (2.0 - 7.5 x 10power9/L), but the remaining 36% were considered neutropenic. The range of neutrophil count that covered 95% of the population was statistically calculated and was found to be 0.5 - 4.4. However, the authors suggested further evaluation of this range by conducting a larger study with a larger sample to represent the whole Sultanate of Oman.