J Eur Acad Dermatol Venereol. 2009 Jun 22; AdıÅen E, Yüksek J, Erdem O, Aksakal F, Aksakal ABackground In acne vulgaris patients, the presence of a dysregulation of the production of innate and specific antimicrobial peptides has been postulated. Objective This study aims to determine whether human neutrophil proteins (HNP) 1-3 are expressed in acne patients. Materials and methods HNP 1-3 expression was investigated in 35 acne patients treated with isotretinoin and in 25 healthy subjects. At the beginning of the study, two skin biopsies were taken from acne patients; one biopsy was taken from an established pustule and one from uninvolved skin, and the biopsies were repeated after treatment. Only one biopsy was obtained from controls. Results The statistical analysis showed that pustular lesions of acne patients had significantly higher levels of perivascular and interstitial HNP 1-3 expression when compared with the biopsy of uninvolved skin of these patients (P = 0.003, P = 0.001, respectively) and with that of healthy controls (P = 0.007, P = 0.014, respectively). Isotretinoin treatment achieved a decrease in the perivascular and interstitial HNP 1-3 expression of pustular lesions (P = 0.01, P = 0.001, respectively). Conclusion Our current study demonstrates the novel observation that a recently identified antimicrobial peptide, HNP 1-3, is expressed in neutrophils of acne inflammation but not in uninvolved skin of these patients. These results suggest that HNP 1-3 may contribute to the development of inflammatory lesions of acne. Conflicts of interest None declared.