Since LYP is also expressed in other cell types, such as B cells, monocytes, neutrophils and dendritic cells (16), the presence of the +1858T allele results in a loss of functional proteins that are unable to regulate T cell activation leading to a hyperresponsive phenotype of T, B and dendritic cells (16,32), thereby having a possible role in the pathogenesis of vitiligo. This evidence concerns the gene PTPN22 and vitiligo.