Monoclonal immunoglobulin deposition disease

Direct deposition of monoclonal light chain and/or, more rarely, fragments of heavy chain may lead to renal failure in myeloma patients.51-53 Renal biopsy reveals nodular sclerosing glomerulopathy. Glomeruli are enlarged with a diffuse and nodular expansion of the mesangial matrix, with little thickening in glomerular basement membrane (GBM). Variable degrees of tubular basement membrane (TBM) thickening, tubular atrophy, and interstitial fibrosis are also present. Immunofluorescent staining shows linear monoclonal light-chain deposit in GBM and TBM in light-chain deposition disease (LCDD). In heavy-chain deposition disease (HCDD) or mixed light/heavy-chain disease (LHCDD), heavy-chain fragment and complement deposits are also present. In about 80% of LCDD, the light chain is of k isotype.54 Both k and X are seen in HCDD, while CH1 constant domain appears to be deleted in the deposits of heavy-chain fragment.55 Commonly, a mixed picture of LCDD and MCN is present. Compared with MCN, monoclonal immunoglob-ulin deposition disease (MIDD) is more likely to lead to nephrotic syndrome, and may precede the diagnosis of myeloma. Systemic light-chain deposition in other organs may occur in some patients.51 The incidence of LCDD appears low. However, in a series of 118 myeloma patients with renal failure who underwent renal biopsy, LCDD was found in 19%.53

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