Novel findings of Langerhans cells and interleukin-17 expression in relation to the acrosyringium and pustule in palmoplantar pustulosis

P>Backgound Palmoplantar pustulosis (PPP) is a chronic and intensely inflammatory skin disease with pustules, erythema and scaling localized to the palms and soles. To date, no specific treatment is known. Earlier findings indicate the acrosyringium as the target for the inflammation. Objectives To identify specific features of the PPP inflammatory cell infiltrate and mediators of inflammation, which might provide insight into the pathogenesis and possible future treatment of the disease. Methods Skin biopsies were taken from 23 patients with typical PPP (23 from involved skin and seven from noninvolved skin) and from 18 healthy controls (10 nonsmokers, eight smokers). Cell infiltrates and inflammation mediators were studied with immunohistochemistry. Results A strong inflammation was observed in lesional skin of PPP. Our main findings of Langerhans cells and interleukin-17 close to or in the acrosyringium differs from findings in psoriasis vulgaris. Other inflammatory cells such as CD4+, CD8+, regulatory T cells and CD11a+ cells were also accumulated close to the sweat duct in epidermis and papillary dermis. More CD4+, CD8+, Langerhans cells, plasmacytoid dendritic cells and a higher proportion of regulatory T cells/CD3+ cells were seen in noninvolved palmar skin from patients with PPP compared with healthy controls. Conclusions Our novel findings indicate that the inflammation in PPP is initiated by the 'stand-by' innate immune system at the acrosyringium.