Hypereosinophilic syndrome.

The hypereosinophilic syndrome is a multisystem syndrome characterized by peripheral blood eosinophilia and eosinophil infiltration of bone marrow, heart, and other organs. The syndrome is associated with cardiac, hematological, pulmonary, neurological, and cutaneous involvement and, if untreated, has a high fatality rate. Criteria for the diagnosis of hypereosinophilic syndrome include (1) peripheral blood eosinophilia with eosinophil counts greater than 1,500/microL for at least 6 months; (2) no evidence of parasitic, allergic, or other known causes of eosinophilia; and (3) presumptive signs and symptoms of multiple organ involvement. Cutaneous manifestations occur commonly but are not diagnostic either clinically or histologically, although the presence of angioedema is a favorable prognostic sign. Because eosinophils are thought to mediate important pathogenic effects, treatment is aimed at controlling peripheral blood eosinophilia.