Observational Multicenter Case-control Study to Assess Nailfold Capillary Abnormalities in Systemic Lupus Erythematosus

The purpose of this study is to investigate the role of nailfold capillaroscopy in the assessment of patients with Systemic Lupus Erythematosus (SLE). Primary endpoint: \- To compare the frequency of major capillaroscopic abnormalities in patients with SLE and healthy controls. Secondary endpoints: * To compare the frequency of major capillaroscopic abnormalities in patients with active and non-active SLE / active SLE and healthy controls / non-active SLE and healthy controls. * To study the association of different capillaroscopic parameters and the status of subjects (SLE / active SLE / non-active SLE / healthy controls).