The hypothesis is that JAK inhibitors can also successfully treat vitiligo. Lesional skin of both alopecia areata and vitiligo primarily contain T cells in a TH1 response as opposed to a mixed cell infiltrate such as in psoriasis or lichen planus. Both alopecia areata and vitiligo are TH1 mediated diseases dependent on the production of IFN-gamma to drive the response. CD8+ T cells are both necessary and sufficient for melanocyte destruction in vitiligo (van den Boorn JG et al 2009) and CD8+NKG2D+ T cells are also necessary and sufficient for hair loss in alopecia areata (Gilhar A et al 2013).