Sequential cryoglobulinemia-associated glomerulonephritis and light-chain amyloidosis in monoclonal gammopathy of renal significance

Kidney disorders associated with monoclonal gammopathy are diagnostically challenging because diverse kidney lesions can occur during the disease course. Here, we report a man in his early 60s who presented with edema, proteinuria, and impaired kidney function. Kidney biopsy revealed cryoglobulinemia-associated glomerulonephritis. Although bone marrow examination showed no increase in plasma cells, the patient was diagnosed with monoclonal gammopathy of renal significance (MGRS) and treated with steroids and cryofiltration, resulting in transient improvement. Later, proteinuria worsened, and kidney function declined despite intensified steroid therapy. A repeat kidney biopsy demonstrated AL (lambda) amyloid deposition in the glomeruli, leading to a diagnosis of AL amyloidosis. This case illustrates that distinct kidney pathologies can emerge sequentially in patients with MGRS and underscores the importance of repeat kidney biopsies when clinical findings change.