Is There Subclinical Synovitis in Patients with Palindromic Rheumatism in the Intercritical Period? A Clinical and Ultrasonographic Study According to Anticitrullinated Protein Antibody Status

Objective. To investigate the presence of subclinical synovitis by ultrasound (US) and the clinical phenotype in patients with palindromic rheumatism (PR) according to anticitrullinated protein antibody (ACPA) status. Methods. Fifty-four patients with PR were studied. Clinical, demographic, serological, and therapeutic characteristics were compared in ACPA-positive and ACPA-negative patients. US searching for synovial hypertrophy (SH) and power Doppler signal (PDUS) in 22 joints of the hands was performed in the intercritical period. The results were compared according to ACPA status and with a healthy control group (n = 30). In 10 patients, US was performed during the joint attack. Results. Most patients were female (63%) with a mean disease duration of 11.6 +/- 10.7 years. Thirty-six patients (66.7%) were ACPA-positive. ACPA-positive patients had a shorter duration of attacks, a younger age, and less knee involvement at disease onset. US examination showed SH grade >= 1 in 79.6% of patients with PR and 50% of controls. Significant US results (SH >= 2 or PDUS) were observed in 2.7% and 1.4% of joints assessed and in 33% and 25.9% of patients with PR, respectively. Only 4 patients (7.4%) had US active synovitis (SH >= 2 plus PDUS) in at least 1 joint. US assessment showed no significant differences between ACPA-positive and ACPA-negative patients. PDUS was observed in 7 out of 10 patients during attacks. Conclusion. Some differences emerged in the clinical phenotype of PR according to ACPA status. Most patients with PR do not have US subclinical synovitis in the intercritical period, even those who are ACPA-positive.