LAUSR

IL: interleukin INTRODUCTION Hypereosinophilic syndromes are rare disorders defined by persistent peripheral eosinophilia (absolute eosinophil count[1.53 10/L) plus evidence of organ involvement. They are subclassified into primary or myeloid hypereosinophilic syndromes, secondary or lymphocytic hypereosinophilic syndromes, and idiopathic. Secondary or lymphocytic hypereosinophilic syndrome is thought to be due to a T-cell population secreting interleukin (IL) 5. Treatment is based on subtype, organ(s) involved, and the presence of genetic targets. First-line therapy for the idiopathic and secondary or lymphocytic hypereosinophilic syndrome variants is systemic steroids. Steroid-sparing options are somewhat limited and not always effective. We present a patientwith recalcitrant idiopathic hypereosinophilic syndromemanifesting as an intensely pruritic eczematous dermatitis who experienced a rapid and remarkable symptomatic response to dupilumab treatment in the setting of concurrent hydroxyurea therapy.