Background/Purpose: Palindromic rheumatism (PR) is characterized by intermittent episodes of arthritis or periarthritis, and it can progress to rheumatoid arthritis (RA), particularly in patients with positive autoantibodies (RF and/or ACPA). Few studies have used ultrasonography (US) to assess joints during symptom-free periods, and most have found no evidence of subclinical synovitis. [1,2]. However, none of these studies have included the feet, specifically the metatarsophalangeal (MTP) joints, which are commonly affected in RA.To assess the presence of subclinical synovitis and erosions by ultrasound (US) during the intercritical phase of seropositive PR and to evaluate the added value of including the feet in the assessment.

Methods: 39 seropositive PR patients (76% female, mean age 54.4 years), 67% received csDMARDs (mainly hydroxychloroquine). Table1.Ultrasound assessment of 1,404 joints revealed synovial hypertrophy (SH ≥2) in 1.7% of joints and 28% of patients; power Doppler signal (PD ≥1) in 1.28% of joints and 23% of patients. US-active synovitis (SH ≥2 plus PD ≥1) was found in 23% of patients. Subchondral bone erosions were detected by US in 0.85% of joints (18% of patients), mostly grade 1. Only two erosions were visible on X-rays. When comparing patients with and without US-active subclinical synovitis, a significantly higher frequency of US-detected bone erosions and use of hydroxychloroquine was observed in the former group (Table 2).

Results: A total of 39 patients (76% female) with seropositive PR were included. The mean age was 54.4 years (±12.6), and the mean disease duration was 9.2 years (±8.5). RF was positive in 23 patients (59%), and ACPA in 32 patients (82%). A total of 26 patients (67%) were treated with csDMARDs, mainly hydroxychloroquine (51%).A total of 1,404 joints (858 in the hands and 546 in the feet) were assessed by US in the 39 patients. Synovial hypertrophy (SH) ≥2 (gray scale) was observed in 24 joints (1.7%)-9 in the hands and 15 in the feet-and in 28% of patients. Power Doppler (PD) ≥1 was observed in 18 joints (1.28%)-9 in the hands and 9 in the feet-and in 9 patients (23%). US-active synovitis, as previously defined (SH ≥2 plus PD ≥1), was observed in 15 joints (8 in the hands and 7 in the feet) and in 9 patients (23.1%).Subchondral bone erosions detected by US were observed in 12 joints (0.85%)-5 in the hands and 7 in the feet (MTP)-corresponding to 7 patients (18%). All US-detected erosions were grade 1 (< 2 mm), except for one case of grade 2 ( >2 mm). Erosions were also observed on X-rays in only two of these cases.When comparing patients with and without US-active subclinical synovitis, a significantly higher frequency of US-detected bone erosions and use of hydroxychloroquine was observed in the former group (Table 2).

Conclusion: In patients with longstanding seropositive PR, significant subclinical active synovitis in at least one joint was observed in 23% of patients during the intercritical period, and US-detected bone erosions were found in 18% of patients, especially in the feet (metatarsophalangeal joints). These findings support that subclinical synovitis and even erosions may be present in patients with PR in the absence of a history of persistent clinical arthritis.

Demographic, clinical, serological, therapeutic and different US findings

Prevalence of US findings in RP patients

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/searching-for-subclinical-synovitis-and-erosions-in-seropositive-palindromic-rheumatism-the-added-value-of-the-ultrasonographic-study-of-feet/