Therefore, Th17 cells have been implicated in the development of various fibrosing diseases of skin and lungs, including ILDs, by enhancing fibroblast proliferation and cytokine production, such as interleukin (IL)-17A, IL-17F, IL-21, IL-22, IL-6 and tumor necrosis factor-α (TNF-α) [27,28]. This evidence concerns the gene IL21 and glycogen storage disease VI.