IL18 and systemic sclerosis: The polymorphisms identified in ACE2 (chrX_15596143), IL-18 (chr11_112014152), IL-18R1 (chr2_103013408), IFNGR1 (chr6_137519588), and IL-2 (chr4_123377482) genes can be considered predisposing factors for the onset of systemic sclerosis.