2. Genetic factors v A high incidence among monozygotic twins(30% x50%), first-degree relative Role of hla-dr4 in the susceptibility to and severity f ra 70%RA patients, a relative risk of having Ra with HLA DR4 of 4 to 5 The susceptibility epitope( shared epitope共同表位) QKRAA或 QRRAA It was considered to be related with the severity of established ra2. Genetic factors ✓ A high incidence among monozygotic twins (30% ~50%),first-degree relative ✓ Role of HLA-DR4 in the susceptibility to and severity of RA − 70% RA patients ,a relative risk of having RA with HLADR4 of 4 to 5 − The susceptibility epitope (shared epitope 共同表位): QKRAA或QRRAA − It was considered to be related with the severity of established RA