Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a powerful negative regulator of T-cell activation. This gene is strongly associated with systemic lupus erythematosus (SLE) [1], [2], [3] as well as other autoimmune diseases including type 1 diabetes [4], rheumatoid arthritis [5], juvenile idiopathic arthritis [6], autoimmune thyroid disease [7], granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis) [8], myasthenia Gravis [9], Hashimotos thyroiditis [10], Graves' disease [11], Addison's disease [12], systemic sclerosis [13], and generalized vitiligo [14]. PTPN22 has strong functional consequences for immune responses, supporting evidence of association with SLE and other autoimmune diseases [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27].
