Natural History of Hypereosinophilia and Hypereosinophilic Syndromes

There is currently no data on the natural history of unexplained chronic hypereosinophilia (HE) and hypereosinophilic syndromes (HES). Clinical practice shows that HE/SHE patients can present 4 evolutionary profiles: A. a single flare-up of their disease, with favourable evolution spontaneously or under corticosteroid therapy, without further recurrence B. recurrent flare-ups with a variable free interval of several months to several years, with or without persistent eosinophilia between flare-ups C. a chronic disease requiring the continuation of a substantive treatment D. chronic asymptomatic HE for years: the mechanisms involved in the occurrence of possible organ damage are unknown The primary objective of the study is to describe the frequency of the different clinical manifestations during the diagnostic and follow-up of the hypereosinophilic syndrome (HES). The primary endpoint is the frequency of the different clinical manifestations and/or organs damage related to eosinophilia.