A "double-seropositive" Vasculitis for antiglomerular basement membrane antibodies and antineutrophil cytoplasmic antibody, and multiple myeloma, all three with simultaneous diagnosis of renal involvement, common pathophysiology, or pure coincidence? first case in the World.

The combination of Goodpasture's disease and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is not exceptional. However, to the best of our knowledge, their association with multiple myeloma (MM) with kidney involvemen thas not been described. We report probably the first case of double-seropositive vasculitis for antiglomerular basement membrane (GBM) antibodies and ANCA associated with MM with renal involvement. A 60- year-old-female presented with severe acute kidney injury. Three months earlier, she had a history of bone pain. Blood workup found a creatinine of 1100 µmol/L and a C-reactive protein of 60 mg/L. Anti-GBM antibodies returned positive at 400 U/mL and pANCA positive at 380 U/mL. Plasma protein immunofixation found a monoclonal immunoglobulin G (IgG) KAPPA peak; the myelogram found a 10% plasmocytosis. On the day 4 of hospitalization, the patient presented with alveolar hemorrhage. The renal biopsy showed diffuse crescentic glomerulo-nephritis with linear glomerular deposits of IgG, with kappa light chain cast nephropathy. The association between vasculitis and malignant blood disease is very rare; the pathophysiology of this association remains unclear. It would seem interesting to look for possible ANCA or anti- GBM activity carried by the monoclonal immunoglobulin.