PTPN22 and systemic lupus erythematosus: PTPN22 also has well-established associations with multiple autoimmune conditions [27], including type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, juvenile idiopathic arthritis [28], Graves' disease [29], [30], systemic sclerosis [31], and alopecia areata [32].