Recent advances in the understanding of genetic defects of neutrophil number and function.

Neutrophils are amongst the first immune cells to arrive at sites of infection and play an important role as the host's first line of defence against invading pathogens. Defects of neutrophil number or function are usually recognized clinically by recurrent infections that often are life-threatening. Over the last few years, a number of genetic mutations have been discovered to be the basis for congenital neutropenia, adding to our understanding of the molecular basis of these diseases. While many genetic mutations that cause severe congenital neutropenia result in a differentiation block at the promyelocyte stage, defects of neutrophil function are more heterogeneous on clinical, genetic and mechanistic levels. In this review we discuss recent advances in our understanding of the genetic and molecular basis of human neutrophil disorders.