Eosinophilic pustular follicular reaction: a paradigm of immune dysregulation

We encountered 10 patients whose biopsies showed an eosinophilic pustular follicular reaction, a histomorphology alleged to be pathognomonic of eosinophilic folliculitis (EF). Only seven of these patients fell within the clinical spectrum of EF. Seven patients had conditions associated with immune dysfunction, including three patients with an atopic history. Potential antigenic stimuli could be elicited in six cases.

Formalin-fixed biopsy specimens from all 10 patients were available for examination. Hematoxylin and eosin-, alcian blue-periodic acid-Schiff (PAS)- and PAS-diastase-stained sections cut from paraffin-embedded tissue were examined by light microscopy. Immunoperoxidase preparations with antibody to IgE were performed on paraffin sections and the number of IgE-decorated cells quantitated in each case. Four patients also had biopsy material submitted in Michel's medium, on which direct immunofluorescent studies were conducted.

IgE-coated mononuclear cells were present in patients whose lesions would logically be expected to derive from dominant type I hypersensitivity mechanisms and absent or minimal in biopsies from those patients in whom the pathogenetic basis of lesions derived principally from cell-mediated immunity.

The eosinophilic pustular follicular reaction, while characteristic of EF, is not exclusive to that entity. It represents an expression of an excessive immediate or delayed-type hypersensitivity reaction to various auto-, epicutaneous, or ingested stimuli. A background of immune dysregulation may be contributory.