Prevalence, phenotype and inheritance of benign neutropenia in Arabs

Background: Benign neutropenia, i.e., neutropenia not associated with an increased risk of infection, may result in serious medical consequences when a 'standard' definition of neutropenia (absolute neutrophil count (ANC) < 1.5 × 10⁹ cells/L) is universally applied to all races. The aims of this study were to determine the prevalence of benign neutropenia among healthy Arabs and evaluate its mode of inheritance. Methods: ANCs were studied prospectively amongst a healthy indigenous population (n = 1032) from the United Arab Emirates undergoing a nation-wide sickle-cell and thalassemia screening program. The mean neutrophil count and the prevalence of benign neutropenia were compared by age, sex and amongst various tribes. Results: The mean neutrophil count (× 10⁹ cells/L) was 3.3 (range 0.95-7.6). Benign neutropenia was present in 110 (10.7%) subjects of whom 24 (2.3%) individuals had moderate neutropenia (ANC 0.5 - 1.0 × 10⁹ cells/L). In the 22 tribe-family groups, the prevalence of benign neutropenia varied between 0% and 38%. Benign neutropenia showed no difference in the frequency amongst the sexes (p = 0.23) and it was independent of age (Spearman's rho = 0.05, p = 0.13). The age-related mean neutrophil count was the lowest in Arabs when compared with other ethnic groups (Blacks, Europeans and Mexicans). The inheritance of benign neutropenia was consistent with an autosomal dominant pattern; however, the diversity of observed phenotypes suggested the presence of more than one genetic variant for this trait. Conclusion: Arabs have ahigh prevalence of benign neutropenia that may be inherited as an autosomal dominant trait.