The trial was conducted over two years across 14 hospitals throughout Spain and involved 70 patients with palindromic rheumatism. The findings, published in Nature Medicine, indicate that abatacept is significantly more effective than hydroxychloroquine in preventing the onset of arthritis.

Palindromic rheumatism is characterized by intermittent episodes of joint inflammation, with acute flare-ups lasting a few days and resolving spontaneously. However, around half of patients eventually develop rheumatoid arthritis, a chronic disease that causes irreversible joint damage. This risk is particularly high in individuals with biomarkers such as rheumatoid factor and anti-citrullinated peptide antibodies. The presence of these two autoantibodies—proteins of the immune system that mistakenly attack the body’s own organs and tissues—is used in the diagnosis of the disease.