Underlying IgM heavy chain amyloidosis in treatment-refractory IgA nephropathy: A case report

BACKGROUND: Monoclonal immunoglobulin can cause renal damage, with a wide spectrum of pathological changes and clinical manifestations without hematological evidence of malignancy. These disorders can be missed, especially when combined with other kidney diseases. CASE SUMMARY: A 61-year-old woman presented with moderate proteinuria with normal renal function. She was diagnosed with IgA nephropathy combined with monoclonal gammopathy of undetermined significance after the first renal biopsy. Although having received immunosuppressive treatment for 3 years, the patient developed nephrotic syndrome. Repeated renal biopsy and laser microdissection/mass spectrometry analysis confirmed heavy chain amyloidosis. After nine cycles of bortezomib, cyclophosphamide and dexamethasone, she achieved very good partial hematological and kidney responses. CONCLUSION: Renal injury should be monitored closely in monoclonal gammopathy patients without obvious hematological malignancy, especially in patients with other pre-existing renal diseases.