When we compared clinical, serological, and genetic features between non-RA CTD and RA-overlapping CTD patients, we found not only the presence of joint symptoms, bone erosion, and RF, which were all included in the 1987 revised ACR criteria [25], but also a higher anti-CCP titer and more prevalent HLA-DRB1 SE in RA-overlapping CTD patients (Table 2). The gene discussed is HLA-DRB1; the disease is rheumatoid arthritis.