Fibronectin glomerulopathy with monoclonal gammopathy responding to bortezomib plus dexamethasone: a case report

BACKGROUND: Fibronectin glomerulopathy is a rare, familial glomerular disease characterized by mesangial fibronectin deposition in the glomeruli. It is caused by the genetic defect in fibronectin and does not involve the activation of the immune system. Therefore, glomerular immunoglobulin and complement staining is generally absent or weak. Monoclonal gammopathy (MG) is an increasing cause of renal lesion, featured by light chain (κ or λ) and/or heavy chain restriction in glomeruli. Herein, we report a case of fibronectin glomerulopathy presenting as strong IgA and C3 immunostaining in renal biopsy, concomitant with monoclonal gammopathy (monoclonal IgA κ). CASE PRESENTATION: A 44-year-old female was admitted to our hospital for one-month pedal edema. The serum albumin of 19.6 g/l, and the 24-h urine protein was 15.092 g. Immunofixation electrophoresis displayed monoclonal IgA. The renal biopsy showed the mesangial deposits positive for IgA (3+) and C3 (3+) and also for IgG (2+), IgM (2+), and C1q (2+) IF microscopy. In addition, the staining intensity of light chain κ was slight greater than that of light chain λ. The glomerular deposits were strongly positive by FN by immuohistochemistry. The patient was treated with bortezomib, dexamethasone in combination with cyclophosphamide and gained partial remission. CONCLUSION: We present the first FNG patient with strong IgA and C3 immunostaining in the context of monoclonal IgA κ in the circulation. Perhaps FNG, monoclonal IgA κ and immune activation are potentially interplayed and eventually induce renal injuries.