[Horton's disease and hypereosinophilic syndrome: a non-fortuitous association]

Giant cell arteritis is a T-cell dependent auto-immune vasculitis that involves a T-helper l (Th1) cell response. We report the unusual case of a woman who developed successively a biopsy-proven temporal arteritis without tissue eosinophilia at age 65, an isolated blood eosinophilia at age 69 and an hypereosinophilic syndrome at age 71, while still taking corticosteroids at the dose of 3mg/day. Considering this temporal relationship, some characteristics of her hypereosinophilic syndrome pointing to a Th2-dependent disease (absence of definite signs of myeloproliferative syndrome, elevated IgE levels and quick normalisation of eosinophil counts under corticosteroid therapy) and the existence of an unexplained blood inflammatory response at the time of HES onset, we postulate that an unbalanced T helper response led in this exceptional case to both diseases.