From the GWAS study, it is believed that several genetic factors may contribute to the susceptibility of MG.[4,22,23] This viewpoint may be supported by the observations on the cytotoxic T-lymphocyte antigen 4 (CTLA-4) and human lymphocyte antigen (HLA)-DQA1 polymorphism which are regarded as independent risk factors in the susceptibility of MG disease. The gene discussed is CTLA4; the disease is myasthenia gravis.