The patient fulfilled both the 2010 ACR/EULAR Criteria for the Classification of RA (arthritis in more than ten joints, elevated levels of ESR and CRP, highly positive RF and ACPA, and disease duration of longer than 6 months) and the 1997 ACR Revised Classification Criteria of SLE (Pericarditis, leukocytopenia/lymphocytopenia, anti-DNA antibody/anti-phospholipid antibody, and anti-nuclear antibody). Here, CRP is linked to rheumatoid arthritis.