Eosinophilic follicular reaction induced by Demodex folliculorum mite: a different disease from eosinophilic folliculitis.

Eosinophilic folliculitis (EF) is an idiopathic dermatitis included in the spectrum of eosinophilic pustular follicular reactions. Demodex folliculorum has been implicated as contributing to the pathogenesis of human immunodeficiency virus-associated EF, but it has not been described outside this context. We present an immunocompetent 65-year-old white man with a 5-year history of recurrent pruritic erythematous and oedematous lesions on his face, neck and scalp. Histopathologically, an eosinophilic microabcess with Demodex folliculorum mite within a pilosebaceous follicle was seen, and considered the causal agent. There were also accumulations of eosinophil granules on collagen bundles, and flame figure formations in the dermis. We believe that 'eosinophilic follicular reaction' is an appropriate term to describe this case of EF induced by D. folliculorum and thus distinguish it from the idiopathic form of EF. Moreover, this case suggests that D. folliculorum can sometimes induce an eosinophilic immune reaction.