Ethnic benign neutropenia: A phenomenon finds an explanation.

Ethnic benign neutropenia (ENP) is the most common form of neutropenia (NP) worldwide, if an absolute blood neutrophil count (ANC) of < 1.5 G/L is used as definition. In 2009, ENP was associated with a gene variation in the ACKR1/DARC gene, the same variation that also confers the Duffy-null trait. In 2017, a novel mechanism for ENP was introduced, questioning if ENP is a true neutropenic state, when the body's total neutrophil count (TBNC) is concerned. Here, we summarize the current knowledge of ENP, asking (1) How well does the peripheral blood ANC predict the TBNC? (2) Can we improve methods for assessing TBNC? (3) Will estimates of TBNC predict infection propensity and reduce the need for further, costly workup?