In addition to family cases due to mutations in genes encoding essential components of the γ-secretase multiprotein complex (PSEN1, PSENEN, and NCSTN genes) [12,13,14,15], several other factors including psychological influences, metabolism, smoking habits, bacterial infections, and associations with other diseases (mainly inflammatory disorders) have been related to a higher incidence of HS [1,2,3,4,5,6,7,8,9,16,29]. This evidence concerns the gene PSEN1 and histiocytic sarcoma.