Eosinophilic Infiltration in Korea: Idiopathic?

osinophilia is defined as the presence of more than 500 eosinophils/ L in the peripheral blood, and may be accompanied by eosinophil infiltration in tissues. Focal eosinophilic infiltration in the lungs and liver is relatively common and is often associated with a parasitic infection, drug hypersensitivity, allergic diseases, collagen vascular diseases, and internal malignancies such as Hodgkin's disease, as well as cancer of the lung, stomach, pancreas or ovary. An eosinophilic abscess refers to a lesion of massive eosinophil infiltration and associated destroyed tissue, and an eosinophilic granuloma refers to a lesion consisting of central necrosis and mixed inflammatory cell infiltrates with numerous eosinophils, a number of neutrophils and lymphocytes, and a palisade of epithelioid histiocytes and/or giant cells. The imaging findings of eosinophilic infiltration in the lungs and liver have mainly been reported by Korean investigators (1 9). There have only been a few case reports (10 13) from Western countries. It is unclear why this is the case and why eosinophilic disease appears to be prevalent only in Korea. Moreover, it is unclear if there are any particular parasitic, allergic, or malignant diseases prevalent in Korea only. Korean authors have addressed the possible causes of eosinophilic infiltration such as idiopathic hypere-osinophilia (1, 2, 4, 6) and malignant tumors through the tumor-associated eosinophilotactic factor (3, 5, 7 9), whereas some authors have offered no explanation (3, 9). Idiopathic hypereosinophilia is a grave disease that is characterized by persistent eosinophilia of 1,500 eosinophils/ L for more than six months, and death before six months due to congestive heart failure (14). However, the course of these patients in our clinical practice is invariably benign. Eosinophilic infiltration of the liver is often associated with cancer of the stomach, liver, etc, but only few of those patients have malignancies (3, 7, 9). Extensive investigations have been to determine if a parasitic infection is the cause of eosinophilic infiltration (9) including Taenia solium (cysticercosis), Paragonimus wester-mani, Clonorchis sinensis, Sparganum mansoni, Anisakis simplex, Fasciola hepatica, Schistosoma, and Toxoplasma gondi. However none of their patients gave positive results. The terminologies are variable and confusing, and include focal eosinophilic infiltration , focal eosinophilic necrosis , focal eosinophilic abscess , eosinophilic granuloma , and foci of eosinophil-related necrosis , etc. However, these terms do not refer to a disease entity but to the histopathologic findings of some diseases with an unknown etiology. Moreover, it is unclear if the …