Background Concomitant presence of systemic lupus erythematous (SLE) and rheumatoid arthritis (RA) in the same patient is known as Rhupus. Poliautoimmunity is not an uncommon phenomenon reported, but only a small series of patients have been described so far with Rhupus. This study aimed to explore the utility of 2019 EULAR/ACR criteria in patients with Rhupus. Methods Cross-sectional study conducted in 11 Rheumatology Departments at Catalonia (Spain). We included prevalent cases classified as Rhupus (RA ACR/EULAR 2010 and SLE-ACR 1997). Data of patients with SLE were selected as control in a ratio 2:1, matched by sex. Results 120 patients were included, 40 Rhupus and 80 SLE alone as controls. 95% were female, with a mean age of 51 yrs and mean of 13 yrs. The 2019 SLE EULAR/ACR criteria were met in 92,5% of the Rhupus and in the 96,3% of the SLE cohort (p>0,05). Numerically, criteria score was higher in those patients with ‘pure’ SLE than Rhupus (21.3 ± 7.0 vs 18.8 ± 6.5, p=NS). Excluding articular domain, there were no significant differences among those who meet new criteria (65% Rhupus vs. 77% SLE (p>0.05)). Proteinuria was the only domain significantly more common in patients with SLE alone. No other differences were found in other clinical or serological characteristics. Conclusion More than 90% of patients classified as Rhupus criteria fulfilled new SLE criteria. This study shows that the new 2019 SLE EULAR/ACR criteria are not useful to differentiate SLE and Rhupus patients. Further investigations are needed to measure their utility in clinical practice for detecting overlap presentation of RA and SLE.
