CXCR4 and neutropenia: Other genes are involved in the pathogenesis of cyclic or intermittent neutropenias, such as solute carrier family 37 member 4 (SLC37A4) [134], vacuolar protein sorting 45 homolog (VPS45) [135,136], C-X-C motif chemokine receptor 4 (CXCR4) [137], CXCR2 [138] serine/threonine kinase 4 (STK4) [139], GATA binding protein 2 (GATA2) [140], and WASP actin nucleation promoting factor (WAS) [141].