Renal involvement in overlap syndrome

Overlap syndrome (OS) is a clinical condition that fulfils the criteria of at least two conjunctive tissue diseases (CTD) occurring in the same patient at the same time or at different moments and its complex clinical picture often makes the diagnosis difficult. Aim. The aim of the study was to evaluate the frequency of renal involvement in a group of patients with overlap syndrome, compared to single CTD. Methods. The observational retrospective study included 122 patients diagnosed with CTD and OS, admitted into Rheumatology Clinic of the Emergency County Clinical Hospital Craiova, between 2011 and 2018, with similar mean age for the two groups (51.41 + 10.88 yo for OS group and 50.78 + 12.65 yo for the other). Results. The proteinuria was significantly lower in the OS group 8% in comparison to the ones without OS (20%) (p = 0.044). The presence of SLE disease and its immunologic changes seems to impact negatively the kidneys, no matter the disease that is associated. Thus, we noticed the presence of renal disease in a percentage of 50% for the patients that associated SLE to SSc, 25% for the ones with SLE and MTCD and 27% for SLE-RA. Conclusions. Although the frequency of renal disease is lower in case of OS, it is important to be recognized, appropriately monitored and integrated in therapeutic decision, especially that some associations are more prone to develop kidney involvement.