Serum Levels of Anti-Cyclic Citrullinated Peptide Antibodies in Patients with Sjögren Syndrome Accompanied by Rheumatoid Arthritis

A 47-year-old woman demonstrated bilateral wrist joint pain during 4 weeks. Her status did not fulfill the ACR classification criteria for RA, and her symptoms had almost disappeared 4 weeks later. After about 1 year, she again complained of tenderness and swelling in the bilateral wrist joints. The laboratory data were as follows: ESR:61 mm/hour, CRP: 1.0 mg/dl, RF: 172 IU/ml, MMP-3: 178.7 ng/ml, and anti-cyclic citrullinated peptide antibodies (aCCP): 488 U/ml. Based on these findings, we diagnosed the patient as having RA. She was treated with several anti-rheumatic drugs, and joint symptoms decreased. This case was regarded as undifferentiated arthritis at the first visit. We later found the high titers of aCCP using her frozen sera after she fulfilled with ACR critera for RA, although aCCP was not checked at first time because its analysis was not covered by national health insurance in Japan. Thus, it is possible that this patient should have been treated as having RA from the first visit. In general, aCCP shows excellent specificity for RA diagnosis although sensitivity is lower. In contrast, it has demonstrated that aCCP is positive in about 40% of patients 1 year before the onset of RA. The clinical outcomes of patients with joint symptoms and positive aCCP analysis, but do not fulfill the ACR criteria for RA, should be assessed in plural patients.