Background/Purpose:  Persistent disease remission is the major goal of Rheumatoid Arthritis (RA) and Psoriatic Arthritis (PsA) treatment. The combined use of clinical and ultrasound selection criteria to define remission status reduces the disease flare rate after treatment tapering or discontinuation in RA but not in PsA patients. The aim of the study was to define the synovial features of RA and PsA patients in clinical and ultrasound remission achieved through combination therapy with Methotrexate and TNF-blockers.

Methods:  RA patients in stable remission (n=22) (DAS<1.6 for at least 6 months), RA patients in stable low disease activity (LDA) (n=8) (1.6<DAS<2.4 for at least 6 months) and PsA patients in stable remission (n=15) (DAS<1.6 and PASI=0 for at least 6 months) achieved by MTX+anti-TNF agents (Adalimumab 40mg or Etanercept 50mg) with Power Doppler (PDUS) negative Synovial Hypertrophy (SH) (confirmed twice 3 months apart) underwent synovial tissue biopsy. RA patients with high/moderate disease activity naïve to any DMARDs (n=50) were included as comparison group. Immunostaining for CD68, CD21, CD20, CD3, CD31 and Collagen was performed.

Results:  PDUS negative RA patients in remission did not differ from PDUS negative RA patients in LDA and PDUS negative PsA patients in remission for age, sex, disease duration, treatment duration and mean dose of MTX or TNF-inhibitor regimen. PDUS negative RA patients in remission showed lower histological scores for synovial CD68⁺ (p=0.001 for lining and sublining), CD20⁺ (p=0.01 for lining and p=0.03 per sublining), CD3⁺ (p=0.01 for lining and sublining), CD31⁺ vessels (p<0.001) and collagen deposition (p=0.03 for lining and p=0.01 for sublining) compared to PDUS positive RA patients naïve to treatment with high/moderate disease activity. However, PDUS negative RA patients in LDA, showed lower histological scores only for sublining CD68⁺ (p=0.03) and CD20⁺ cells (p=0.05), lining CD3⁺ cells (p=0.04), CD31⁺ vessels (p<0.001) and sublining deposition of collagen (p=0.05) compared to PDUS positive RA patients naïve to treatment with high/moderate disease activity. In addition, there was no significant difference in terms of lining and sublining CD68⁺, CD20⁺, CD3⁺, CD31⁺ cells and collagen comparing PDUS negative RA patients in remission and in LDA respectively. On the contrary, PDUS negative PsA patients in remission did show higher histological scores for sublining CD68⁺ (p=0.04) and CD3⁺ cells (p=0.04) as well as CD31⁺ vessels (p=0.01) than PDUS negative RA patients in remission.

Conclusion:  PDUS negative RA patients in remission have comparable synovial histological features compared to PDUS negative RA patients in LDA. However, PsA patients in remission are characterized by higher degree of residual synovial inflammation compared to RA patients in remission despite PDUS negativity after TNF-inhibition success.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/synovial-features-of-rheumatoid-arthritis-and-psoriatic-arthritis-differ-in-patients-in-clinical-and-ultrasound-remission-after-anti-tnf-therapy/