The diagnostic challenge of patients with anti-U1-RNP antibodies

• Published in: Rheumatology international 2023-03, Vol.43 (3), p.509-521
• Main Authors: Elhani, Ines, Khoy, Kathy, Mariotte, Delphine, Comby, Elisabeth, Marcelli, Christian, Le Mauff, Brigitte, Audemard-Verger, Alexandra, Boutemy, Jonathan, Maigné, Gwénola, Martin Silva, Nicolas, Aouba, Achille, de Boysson, Hubert
• Format: Article
• Language: English
• Subjects: Medicine; Medicine & Public Health; Observational Research; Rheumatology
• ISSN: 1437-160X; 1437-160X
• DOI: 10.1007/s00296-022-05161-w

Anti-U1-RNP antibodies are necessary for the diagnosis of mixed connective tissue disease (MCTD), but they are also prevalent in other connective tissue diseases, especially systemic lupus erythematosus (SLE), from which distinction remains challenging. We aimed to describe the presentation and outcome of patients with anti-U1-RNP antibodies and to identify factors to distinguish MCTD from SLE. We retrospectively applied the criteria sets for MCTD, SLE, systemic sclerosis (SSc) and rheumatoid arthritis (RA) to all patients displaying anti-U1-RNP antibodies in the hospital of Caen from 2000 to 2020. Thirty-six patients were included in the analysis. Eighteen patients (50%) satisfied at least one of the MCTD classifications, 11 of whom (61%) also met 2019 ACR/EULAR criteria for SLE. Twelve other patients only met SLE without MCTD criteria, and a total of 23 patients (64%) met SLE criteria. The most frequent manifestations included Raynaud’s phenomenon (RP, 91%) and arthralgia (67%). We compared the characteristics of patients meeting only the MCTD ( n  = 7), SLE ( n  = 12), or both ( n  = 11) criteria. Patients meeting the MCTD criteria were more likely to display SSc features, including sclerodactyly ( p