Wells' syndrome.

Eosinophilic cellulitis/Wells' syndrome is a rare dermatosis with erythematous, urticarial plaques that become more indurated and eventually have grey blue discoloration. The histopathology is distinctive, with a diffuse infiltrate composed predominantly of eosinophils but admixed with lymphocytes, histicytes and occasionally multinucleated histiocytes. There is dermal edema with so called "flame figures" that is composed of collagen focally enveloped with aggregates of eosinophilic granules. These collagen fibres may be surrounded by palisading histiocyes. The course is variable with waxing and waning and eventual spontaneous resolution.