[The unusual mimicker of a polymyositis].

This article describes a hantavirus-associated pronounced myositis as a rare differential diagnosis to polymyositis. The literature on the pathogenesis of hantavirus disease discusses less a direct viral cytopathology but more a secondary immune dysregulation with induction of a capillary leak. This article describes for the first time a case of successful treatment of protracted hantavirus myositis using high-dose glucocorticoids and cyclophosphamide, followed by ciclosporin and MTX.