Background/Purpose: Finger extensor tendon involvement (FEP) or paratenonitis has previously been described by ultrasound (US) in patients suffering from early psoriatic arthritis. Contradictory results were published in patients suffering from rheumatoid arthritis.

We aimed to assess the involvement of FEP in early rheumatoid arthritis (ERA) patients and in asymptomatic subjects.

Methods: Inclusion criteria for ERA patients were: symptom duration < 6 months prior to ERA diagnosis; age >18 years; no DMARD treatment at time of US examination. Inclusion criteria for asymptomatic subjects group were: age >18 years; no other known rheumatic disease (connective tissue diseases, rheumatoid, psoriatic arthritis, spondyloarthritis, hand osteoarthritis, gout, chondrocalcinosis); no psoriasis, no inflammatory bowel diseases. Patients were evaluated clinically (44-tender and 44-swollen joint count), and answered health assessment questionnaires (HAQ). Hand, wrist, feet X-ray and laboratory tests including anti-citrullinated protein antibodies (ACPA), rheumatoid factor (RF) and C-reactive protein (CRP) were performed in all patients. US assessments were performed blinded to clinical and laboratory data. FEP was assessed in longitudinal and in transverse view at all metacarpophalangeal (MCP) joints and proximal phalangeal joints, both in grey-scale and Doppler mode. FEP was defined as abnormal anechoic and/or hypoechoic (relative to tendon fibers) paratenon widening seen in two perpendiculars planes and was scored as present/absent.

Results: One hundred and four consecutive ERA patients and 44 asymptomatic subjects were included in this study. Mean age and comparable gender distribution were observed between the groups (50.1±1.3 y, ERA vs. 45.8±2.0 y, asymptomatic subjects). ACPA were present in 63.5%, RF in 62.5%, tobacco use in 22.1% and x-ray bone erosions in 33.7% of ERA patients. Age, gender, delay between the first symptom and diagnosis, SDAI, CDAI, CRP level, HAQ did not differ significantly between patients with FEP involvement and those without. FEP was present in two-third of ERA patients and absent in asymptomatic subjects (60.6% vs. 0%, p< 0.001). In univariate analysis, the presence of FEP was significantly associated with the presence of MCP erosion (p=0.02), ACPA positivity (p=0.017), rheumatoid factor (p=0.009) and tobacco use (p=0.015). In multivariate analysis, the presence of FEP was significantly associated with the presence of MCP erosions, ACPA positivity and tobacco use (p< 0.01).

Conclusion: FEP is relatively frequent in ERA patients and it is not present in asymptomatic subjects. Our results show that FEP is associated with ACPA positivity and bone erosions, thus identifying patients early with a possibly more aggressive or severe disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/digital-extensor-paratenonitis-is-frequent-in-early-rheumatoid-arthritis/