Natural History of Hypereosinophilia and Hypereosinophilic Syndromes

Unexplained chronic hypereosinophilia (HE) and hypereosinophilic syndromes (HES) are heterogeneous regarding the organ involvements (heart, lungs, skin, .. or none), the evolutionary profiles, the response to treatments. Underlying mechanisms are largely unknown and may associate genetic predisposing factors (germinal ? somatic?), environmental factors (alimentation, tobacco use, hormones, infections, ..) The COHESion study aims to study all clinical and biological characteristics of HE/HES patients and their evolutionary profiles, with a focus on genetic factors and the mechanisms supporting transitory or persistant chronic HE/HES (in absence of any well identified extrinsic trigger like drugs, parasitosis, ..)

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.