The double shared epitope: Its impact on clinical features and ultrasound findings in rheumatoid arthritis

ObjectivesThe link between the HLA-DRB1 locus and the risk of rheumatoid arthritis (RA) shown in genome-wide association studies strengthens the shared epitope (SE) hypothesis. We aimed to assess the impact of the double dose of the SE (double SE) on RA and explore its clinical associations, including the response to abatacept.MethodsWe evaluated RA patients treated with csDMARDs or abatacept for HLA-DRB1 typing, clinical characteristics at baseline, and disease activity and ultrasound findings over 12 months.ResultsPatients with the double SE (n = 12) had significantly higher anti-citrullinated protein antibody (ACPA) titers, higher total grayscale (GS) score, and power Doppler (PD) score at baseline than patients without the double SE. Patients with the double SE exhibited reduced rates of SDAI remission and pronounced improvements in multiple disease activity between baseline and 12 months, including SDAI, CDAI, total GS score, and total PD score. When focusing on abatacept-treated patients, the decreases in SDAI, CDAI, and total PD score between baseline and 12 months were significantly larger in patients with the double SE.ConclusionsPatients with the double SE exhibited distinct characteristics, increased disease activity, and improved response to abatacept treatment.