Inflammatory cells, cytokines and matrix metalloproteinases in amicrobial pustulosis of the folds and other neutrophilic dermatoses

Amicrobial pustulosis of the folds (APF) is a rare cutaneous disease characterized by relapsing sterile pustules frequently associated with autoimmune disorders. Although APF pathophysiology is still undefined, scattered reports suggest involvement of neutrophils. The aim of the present study is to evaluate the role of the skin inflammatory infiltrate, selected multifunctional cytokines and effectors of tissue damage in APF and other neutrophilic dermatoses. We studied, by immunohistochemical methods, inflammatory cell markers (CD3, CD163, myeloperoxidase), cytokines (TNF-alpha, IL-8, IL-17), metalloproteinases (MMP-2, MMP-9) and vascular-endothelial-growth-factor (VEGF) in lesional skin from six patients with APF, 11 with pyoderma gangrenosum (PG), 7 with Sweet's syndrome, and in 20 normal skin samples. Immunoreactivities of CD3, CD163, myeloperoxidase, TNF-alpha, IL-8, IL-17, MMP-2, MMP-9 and VEGF were significantly higher in APF, PG and Sweet's syndrome than in controls (p=0.0001). IL-8 was more expressed in PG than in APF (P=0.002) and Sweet's syndrome (p=0.001). In APF, MMP-9 reactivity was higher than in Sweet's syndrome (p=0.035), but less intense than in PG (p=0.020). Our study supports the role of proinflammatory cytokines/chemokines and MMPs as important effectors for the tissue damage in APF similarly to classic neutrophilic dermatoses.