Rhupus syndrome: assessment of its prevalence and its clinical and instrumental characteristics in a prospective cohort of 103 SLE patients.

The term "rhupus" is traditionally used to describe patients with coexistence of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). The aim of the present work was to investigate prevalence, clinical and radiological picture as well as the serological profile of a series of rhupus patients; SLE patients and RA patients from our Unit were used as disease control groups. A total of 103 consecutive SLE patients were screened; among the entire cohort, 10 patients (9.7%) were classified as "rhupus". In our rhupus patients SLE features preceded the onset of arthritis in 5 patients (50%) while in the remaining patients arthritis appeared before or simultaneously (3 and 2 patients respectively). As compared with SLE patients, rhupus patients have significantly less kidney involvement (p=0.01) while no differences were observed between neuropsychiatric, cutaneous, hematological involvement or serositis. At our physical examination, 9 (90%) rhupus patients were presenting active joint involvement; CRP positivity and ESR levels resulted significantly higher than in SLE (p=0.006) patients while no differences were observed with respect to RA patients. In all rhupus patients, at least one pathological finding was revealed by ultrasound (US) examination at wrist and/or hand joints; overall, rhupus patients presented higher scores in all the US parameters with respect to SLE patients, especially at hands; no statistically significant differences have been observed with respect to RA patients. Magnetic resonance (MR) revealed erosions in all rhupus patients with a concomitant bone edema in five patients. The cumulative erosive burden in rhupus patients was significantly higher than in SLE patients and similar to RA patients (SLE vs rhupus p=0.005); bone pathology distribution was also similar between rhupus patients and RA patients. These data suggest the importance of assessing joint involvement in SLE with advanced imaging techniques and of evaluating the presence of prognostic factors for joint disease severity in order to establish adequate disease monitoring and to institute early appropriate therapies to avoid late consequences of unrecognized concomitant rheumatoid arthritis (Amezcua-Guerra et al., 2006 [25]; Zhao et al., 2009 [26]).