Background Concomitant presence of two autoimmune diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) is known as Rhupus. Despite, poliautoimmunity is not uncommon described in patients with systemic autoimmune diseases, only a small series of patients have been described so far with Rhupus. Our purpose was to analyze clinical and serological characteristics of patients with Rhupus and compare them with a cohort of patients with SLE.

Methods In this cross-sectional study, we included cases of Rhupus (RA-ACR/EULAR 2010 plus SLE-ACR 1987 criteria) from different Rheumatology Departments at Catalonia, Spain. In addition, we included patients with diagnosis of SLE in a 2:1 ratio matched by sex and race. All information was recorded following an established protocol.

Results A total of 57 patients were included, 19 cases with Rhupus and 38 cases of SLE alone as controls. 93% of patients were female, Caucasian represented 71.4%, Mestizo 17.9% and 5.4% were Asian. Mean age was 48.6±13.5 years and mean disease duration was 11.48±9.1 years. Main clinical characteristics were cutaneous involvement (75.0%), hematological (66.0%), serositis (19.3%), renal disease (17.9%) and secondary Sjögren syndrome (28%) among others. Clinical and serological characteristics according groups are shown in table 1.

Conclusions We found some clinical and serological differences among patients with Rhupus and SLE alone. As expected, articular domains and titers of RF and ACPAs were higher in Rhupus and they are more commonly treated with methotrexate and rituximab. By other hand, leukopenia, oral ulcers, anti-Ro antibodies and higher SLEDAI score were more common among SLE patients. Whether Rhupus patients represent a different condition requires further analysis in bigger cohorts.