What do laboratory studies and joint radiographs show in palindromic rheumatism?
The ESR and other acute-phase reactants may be elevated during attacks but are normal between them. Rheumatoid factor (RF) and anticyclic citrullinated peptide (anti-CCP) are positive in 30% to 50% of cases and identify patients who will eventually develop RA. Antinuclear antibodies (ANAs) are typically negative and serum complement levels are normal. There have been few studies of synovial fluid in palindromic rheumatism. Leukocytes may vary from a few hundred to several thousand, with the magnitude poorly correlated with symptom severity. Radiographs show only soft tissue swelling. Similar to intermittent hydrarthrosis, some patients (10%) have been found to be heterozygous for mutations of the MEFV gene similar to those reported in FMF.