Systemic lupus erythematosus (SLE) and small-sized vessel vasculitis are usually two distinguishable autoimmune diseases. However, a vasculitis may be found in the course SLE but rarely corresponds to an ANCA-associated vasculitis (AAV). We report four cases of de novo SLE associated with AAV, our aim being to discuss the clinical significance of this association. We included four patients fulfilling the criteria for both SLE and AAV and followed in two different university hospitals between 1996 and 2009. In light of a 20-year literature review (25 described clinical cases), we discussed the etiopathogeny of such an association. All patients presented a severe renal involvement (creatininemia ranging from 120 to 370 μmol/l) and thrombopenia (ranging from 45,000 to 137,000 platelets/mm(3)). The other main clinical symptoms were arthritis (n = 3), serositis (n = 2) and intra-alveolar hemorrhage (n = 2). An inflammatory syndrome was noticed at diagnosis in all cases. ANCAs were MPO-ANCAs in all cases. Two out of these four patients were also diagnosed with antiphospholipid syndrome. The frequency of this association seems not fortuitous. Although the etiopathogenic mechanisms of such an association remain to be more precisely described, several clinical, histological and immunological features support the hypothesis of the existence of a SLE-AAV overlapping syndrome. Moreover, clinicians must be aware of such an overlapping syndrome, notably because its initial presentation can be very severe.