Guggino et al. investigated the involvement of Th9 in the development of systemic sclerosis (SSc) [93], demonstrating the upregulation of the IL-9/IL-9R axis components, including IL-9, IL-9R, IL-4, TSLP, and TGF-β, in the inflamed skin of SSc individuals. This evidence concerns the gene IL4 and systemic sclerosis.