On the other hand, PTPN22 R620W appeared to have a loss-of-function effect in the context of myasthenia gravis (9), and Zikherman et al demonstrated that overexpression of Csk as well as PTPN22 R620W revealed a loss-of-function effect for the SNP (10). The gene discussed is PTPN22; the disease is myasthenia gravis.