A patient with persistent renal AL amyloid deposition after clinical remission by HDM/SCT therapy

A 62-year-old female patient was admitted to our hospital for evaluation of nephrotic syndrome. Monoclonal gammopathy (IgG λ type) and urinary Bence Jones proteins were detected in the serum and urine by the immunofixation method. The initial renal biopsy revealed amyloid deposition in mesangial area, glomerular capillary walls and arterioles by Congo-red staining, and amyloid fibers were detected by electron microscopy. On the bone marrow test, plasma cells accounted for 8.6%. Based on these findings, we diagnosed as AL amyloidosis associated with multiple myeloma. We treated her by high-dose intravenous injection therapy of melphalan combined with autologous peripheral blood stem cell transplantation. She achieved complete hematologic response 27 months later, however. Urine M-protein disappeared 2 months after treatment, and proteinuria slowly disappeared 17 months after treatment. On the other hand, amyloid fibers remained in renal biopsied tissues at 17 and 53 months after therapy. Electron microscopic examination also revealed the similar amyloid fibers in glomeruli. These findings suggest that, in this case, immunoglobulin light chains may cause directly and/or indirectly glomerular epithelial injury and nephrotic range proteinuria rather than via amyloid fiber formation.