Background/Purpose: Palindromic rheumatism (PR) may evolve to rheumatoid arthritis (RA), especially in anti-citrullinated peptide/protein antibody (ACPA) positive patients, although many do not evolve to RA after long-term follow-up. It is unclear whether ACPA-positive patients have more subclinical synovitis during the intercritical phase and whether this is a risk factor for progression to RA. There are no data on different ACPA specificities in PR compared with RA

Objectives:To analyze differences in the presence of subclinical synovitis in PR patients according to ACPA status and determine whether fine specificities of citrullinated peptides differ between PR and RA.

Methods: Patients with pure PR (*Guerne et al criteria) with no progression to chronic rheumatic disease at study entry were included. Clinical, demographic, serological and therapeutic variables were collected. Subclinical synovitis (grade≥ 2 synovial hyperplasia plus Doppler signal) in the intercritical period was analyzed by ultrasound of both hands. ACPA specificities were assayed by home-made ELISA tests using chimeric fibrin/filaggrin (CFFCP1), fibrin/vimentin (CFVCP), and vimentin/fibrin (CVFCP) citrullinated chimeric synthetic peptides in pure PR patients who were positive for commercial CCP2 tests: results were compared with controls with established RA (1987 ACR criteria)

Results: Fifty-seven patients (64.9% female, mean age 51.6±11.2 years and mean disease duration 11.9±10.5 years) with pure PR were included: 39 (68.4%) were ACPA+ (CCP2 test). No significant clinical differences were observed between ACPA+ and ACPA- patients except for a shorter duration of attacks and greater DMARD use (mainly hydroxychloroquine) in ACPA+ patients. RF was most-frequently found in ACPA positive patients. Subclinical synovitis by ultrasound was observed in 16 patients (28.1%), most-frequently in the metacarpal joints and wrists, without significant differences between ACPA+  and ACPA+ PR patients (30.8 vs. 22.2% p=0.51).

Citrullinated peptide specificities did not significantly differ between CCP2+ PR patients (n=39) and control patients (n=39) with established CCP2+ RA (66.7% female, mean disease duration 7.2±4.4 years), although there was a trend to a higher number of specificities and a higher titer of ACPAS in RA patients (Table 1)

Table 1 Frequency of citrullinated peptide specificities in CCP2-positive PR and RA patients.

	PR-CCP2 positive n=39	RA-CCP2 positive n=39	p value
CCP2 levels(IU/L)	467.72±513.6	761.74 ±595.7	0.09
CFFCP1 n (%)	29 (74.4%)	35 (89.7%)	0.24
CFVCP n (%)	24 (61.5%)	26 (66.7%)	0.6
CVFCP n (%)	29 (74.4%)	34 (87.2%)	0.43
CFFCP1 levels (ODU)	1.01±0.97	1.25±0.88	0.24
CFVCP levels (ODU)	0.59±0.54	0.65±0.60	0.25
CVFCP levels (ODU)	0.82±0.80	0.89±0.66	0.24
≥2 Specificities	28 (71.7%)	35 (89.7%)	0.2
3 Specificities	23 (59%)	25 (64.1%)	0.7

ODW: optic density units

Conclusion: ACPA are frequently found in patients with PR. Most PR patients do not have subclinical synovitis (by ultrasound), which is not associated with ACPA status, in the intercritical period. No significant differences in the different specificities of ACPAS were observed between PR and RA, suggesting that chronic PR might be considered an abortive form of RA

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-citrullinated-peptideprotein-antibody-specificities-and-subclinical-synovitis-in-palindromic-rheumatism-towards-a-better-understanding-of-the-relationship-with-rheumatoid-arthritis/