Eosinophilic pustular folliculitis: The transition in sex differences and interracial characteristics between 1965 and 2013

Eosinophilic pustular folliculitis (EPF) is characterized by a non-infectious infiltration of eosinophils in the hair follicles. It has three variants: (i) classic EPF; (ii) immunosuppression-associated EPF, which herein is subdivided into HIV-associated (IS/HIV) and non-HIV-associated (IS/non-HIV); and (iii) infancy-associated EPF (I-EPF). The rarity of EPF has hindered our understanding of this entity. To examine the characteristics of EPF, with respect to age, sex, race, and chronology, published in case reports to date, we queried PubMed using the following terms: (eosinophilic pustular folliculitis [All Fields] OR eosinophilic folliculitis [All Fields]) AND (1965/1/1 [PDAT]: 2013/12/31 [PDAT]). Additional Japanese cases were collected from Igaku Chuo Zasshi through Ichushi-Web, JDream III, and secondhand quotations from domestic periodicals published in Japan. Proceedings were excluded. The PubMed search produced 275 citations containing 358 cases of EPF (224 men, 132 women, and two of unspecified sex); these cases involved classic EPF (101 Japanese and 81 non-Japanese), IS/HIV (4 Japanese and 85 non-Japanese), IS/non-HIV (4 Japanese and 20 non-Japanese), and I-EPF (4 Japanese and 59 non-Japanese). Ichushi generated an additional 148 citations containing 207 cases of Japanese (148 men and 59 women), which included cases of classic EPF (181 cases), IS/HIV (14 cases), IS/non-HIV (9 cases), and I-EPF (3 cases). There was no sex difference in the classic EPF cases reported between 2003 and 2013, whereas IS/HIV, IS/non-HIV, and I-EPF were predominated by men. There is room for reconsideration of sex differences, particularly with regard to classic EPF. The rarity and specificity of I-EPF in Japan may reflect a state of uncertainty about this entity.