Our previous studies on the characterization of anti-TNF-α-induced paradoxical psoriasis reactions revealed an overactivation of innate immunity in the skin lesions of HS patients, also due to a strong predisposition of HS patients to develop immune responses against innate stimuli, and the presence of an immunological infiltrate mainly represented by BDCA2+ plasmacytoid dendritic cells (pDCs), CD15+ neutrophils, c-kit/CD117+ mast cells, CD68+ macrophages and monocytes (17). This evidence concerns the gene KIT and histiocytic sarcoma.