Coexistence of cryoglobulinemia and ANCA-associated vasculitis in a chronic brucellosis patient -a case report and literature review.

BACKGROUND: The renal involvement of brucellosis is not common. Here we reported a rare case of chronic brucellosis accompanied by nephritic syndrome, acute kidney injury, the coexistence of cryoglobulinemia and antineutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) superimposed on iliac aortic stent implantation. The diagnosis and treatment of the case are instructive. CASE PRESENTATION: A 49-year-old man with hypertension and iliac aortic stent implantation was admitted for unexplained renal failure with signs of nephritic syndrome, congestive heart failure, moderate anemia and livedoid change in the left sole with pain. His past history included chronic brucellosis and he just underwent the recurrence and completed the 6 weeks of antibiotics treatment. He demonstrated positive cytoplasmic/proteinase 3 ANCA, mixed type cryoglobulinemia and decreased C3. The kidney biopsy revealed endocapillary proliferative glomerulonephritis with a small amount of crescent formation. Immunofluorescence staining revealed only C3-positive staining. In accordance with clinical and laboratory findings, post-infective acute glomerulonephritis superimposed with AAV was diagnosed. The patient was treated with corticosteroids and antibiotics and sustained alleviation of renal function and brucellosis was achieved during the course of a 3-month follow-up. CONCLUSIONS: Here we describe the diagnostic and treatment challenge in a patient with chronic brucellosis related glomerulonephritis accompanied by the coexistence of AAV and cryoglobulinemia. Renal biopsy confirmed the diagnosis of postinfectious acute glomerulonephritis overlapping with ANCA related crescentic glomerulonephritis, which was not ever reported in the literature. The patient showed a good response to steroid treatment which indicated the immunity-induced kidney injury. Meanwhile, it is essential to recognize and actively treat the coexisting brucellosis even when there are no clinical signs of the active stage of infection. This is the critical point for a salutary patient outcome for brucellosis associated renal complications.