DEFB4A and histiocytic sarcoma: Nine β-defensin genes, including DEFB4 (Defensin Beta 4A) and DEFB103 (Defensin Beta 103B), encoding for proinflammatory mediators human β-defensin-2 and human β-defensin-3, respectively, exist as a cluster presenting copy number variations; the same authors confirmed, in two independent cohorts, that the presence of more than six defensins cluster copy number had an increased risk of developing HS, whereas the presence of fewer than six copies was linked with early-onset disease, and fewer areas affected and less frequent presentation of permanent purulence of the skin lesions [74].