Rapidly progressive glomerulonephritis due to systemic lupus erythematosus and ANCA-associated vasculitis overlap.

Systemic lupus erythematosus (SLE) and ANCA-associated vasculitis (AAV) are different autoimmune diseases. While vasculitis can be seen in the SLE clinical course as a secondary phenomenon, and may indicate a severe disease, primary vasculitis such as AAV rarely occurs in association with SLE. We present a 44-year-old woman who presented with rapidly progressive glomerulonephritis which was histologically identified as a combination of crescentic and lupus nephritis in the presence of myeloperoxidase ANCA antibody. The frequency of this association is very rare. The clinical, histological and immunological features are different in SLE/AAV overlap syndrome and need different treatment options, which may include rituximab, to achieve complete recovery. Since SLE/AAV overlap can be serious at presentation, the physician must be aware of this syndrome.