ABSTRACT
Hypereosinophilic syndrome is a rare disease characterized by marked peripheral eosinophilia and eosinophilic infiltration of many organs such as heart, lung, central nervous system, liver and spleen. This disease is defined by following criteria. First, sustained blood eosinophilia is greater than 1,500/mm3 longer than 6 months. Second, other apparent etiologies for eosinophilia must be absent, including parasitic infestation and allergic disease. Third, patients must have signs and symptoms of organ involvement. In Korea, some cases that eosinophil infiltrated lung, liver, gastrointestinal tract or skin were reported. In this report, we found a case showing myalgia, fatigue and eosinophilia in periodic health examination, and diagnosed hypereosinophilic syndrome.