Two cases of infancy associated eosinophilic pustular folliculitis (I-EPF) comparing the profile of infiltrating cells with classic EPF by immunohistochemical study

Infancy associated eosinophilic pustular folliculitis (I-EPF) is a clinical variant of EPF that develops in childhood. Previous studies have suggested that I-EPF exhibits clinical and histological differences distinct from other variants, including classic EPF. Herein, we report two patients with I-EPF treated with topical indomethacin. These two cases exhibited less perifollicular and more perivascular eosinophilic infiltration, which is different in distribution from that of classic EPF. Immunohistochemical study demonstrated that the infiltrating mononuclear cells were CD4-dominant T cells in classic EPF and I-EPF, whereas the number of CD68-positive cells was significantly higher in classic EPF than in I-EPF. Immunohistochemical staining was also performed for eosinophilic pustular folliculitis (HPGDS), which has been reported to induce eosinophils and is a therapeutic target of indomethacin in classic EPF. HPGDS-positive cells were also observed in I-EPF, which may explain the effectiveness of topical indomethacin. Although clinical and histopathological features of I-EPF are different from other variants, the arachidonic acid pathway could be involved in eosinophil infiltration, not only in classic EPF but also in I-EPF.