A previous study reported that eosinophilia was observed in 31% of WAS patients.[3] Lexmond et al confirmed that this hematological characteristic resulted from the Tregs dysfunction caused by WASp deficiency, which weakened the suppressive function of Tregs on Th2 cell differentiation and consequently caused eosinophilia.[35]. The gene discussed is WAS; the disease is Wiskott-Aldrich syndrome.