Dual anti-neutrophil cytoplasmic antibody and anti-glomerular basement membrane antibody-positive crescent glomerulonephritis in a patient with monoclonal gammopathy of undetermined significance: A case report

RATIONALE: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and anti-glomerular basement membrane (GBM) antibody disease are both rare autoimmune diseases. Monoclonal gammopathy of undetermined significance (MGUS) is one of the most common causes of plasma cell dyscrasias (PCD). The three entities can cause renal lesions via different mechanisms and, however, they have not been reported in a single patient with renal lesion. PATIENT CONCERNS: Here, we describe a patient with half-year fatigue and 40-day nausea and vomiting. Laboratory workup displayed increased serum creatinine, proteinuria, and mild microscopic hematuria. Serological tests were positive for anti-nuclear antibody (titer 1:100), anti-GBM antibodies (not quantified), and myeloperoxidase (MPO)-ANCA (228 RU/ml). Serum immunofixation electrophoresis found monoclonal immunoglobulin (MIg) G κ-light chain in the serum. Renal biopsy displayed crescentic formation in glomerule by microscopy and staining for liner IgG (+), sparse C3 (+-) and light chain (κ and λ) (+-) by immunofluorescence. The bone marrow examination indicated basically normal myelogram and sporadic plasma cells positive for CD38, CD138 staining, and κ light-chain restriction. DIAGNOSIS: Crescentic glomerulonephritis and MGUS. INTERVENTIONS: The patient was treated with plasmapheresis, pulse methylprednisolone therapy in combination with cyclophosphamide. OUTCOMES: The patient still became hemodialysis-dependent. LESSONS: The present study discusses, to the best of our knowledge, first case of crescentic glomerulonephritis seropositive for ANCA anti-GBM antibody in MGUS. The rare concurrence highlights it as a clinical concern.