Pauci-immune necrotizing and crescentic glomerulonephritis in a patient with systemic lupus erythematosus

We report a case of pauci-immune proliferative necrotizing and crescentic glomerulonephritis in a patient with systemic lupus erythematosus (SLE) who presented with a nephrotic syndrome, while SLE was clinically and serologically quiescent. Immunofluorescence and electron microscopy examination of the kidney biopsy failed to reveal any significant deposit of immunoglobulins as well as of complement C3 and C1q, excluding lupus nephritis as the determinant of crescentic glomerulonephritis. Anti-myeloperoxydase (MPO) as well as anti-proteinase 3 (PR3) antibodies were absent in the serum. An immunosuppressive regimen including corticosteroids and IV cyclophosphamide led to a dramatic decrease of proteinuria. We conclude that necrotizing glomerulonephritis unrelated to lupus nephritis may occur in a patient with quiescent SLE. An underlying dysfunction of cell-mediated immunity might explain the association of pauci-immune crescentic glomerulonephritis and SLE.