An increased white blood cell count is a hallmark of active Kawasaki syndrome (KS) and has been suggested as a risk factor for cardiovascular morbidity by several investigators. Morphologic analysis of polymorphonuclear cells (PMNs) represents an accessible tool that is worth validating prospectively in a larger study to predict KS severity and poor response to intravenous immunoglobulin. More precisely, PMNs might be culprits in the development of KS and its complications, but they are not the only cells involved in this systemic vasculitis: further in-depth analysis will probably unravel the tangled pathogenesis of KS and find new targets for a more specific therapy.