Rhupus syndrome: Description of 9 cases with special attention to the HLA-DR genotype.

Background and objectives: Rhupus is a very rare syndrome of overlapping rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), characterized by the presence of erosive polyarthritis associated with symptoms and signs of SLE and the presence of high specificity autoantibodies. The analysis of HLA-DR molecules would allow us to genetically characterize patients diagnosed with rhupus, being able to differentiate them from the HLA-DR profile of patients with RA and SLE.

Materials and methods: Cross-sectional observational study of 9 patients diagnosed with rhupus in whom the HLA-DR genotype was genetically characterized.

Results: Rhupus is usually more frequent in women with initial diagnosis of RA. The most frequent clinical manifestations are articular and, serologically, ANA, RF and anti-CCP positivity stand out. The most frequent HLA-DR were HLA-DR1, HLA-DR3, HLA-DR4, HLA-DR7 and HLA-DR13.

Conclusions: A higher proportion of HLA-DR1 and DR9 was observed in patients with rhupus compared to RA and SLE, as well as a lower proportion of HLA-DR2, DR6 and DR8, which would help the early characterization of these patients prior to the overlap diagnosis.