Renal monoclonal immunoglobulin deposition disease: The disease spectrum

This study report's the clinicopathologic findings and outcome in 34 patien ts with renal monoclonal immunoglobulin deposition disease (MIDD), which in cluded 23 light-chain DD (LCDD), 5 light- and heavy-chain DD (LHCDD), and 6 heavy-chain DD (HCDD). A total of 23 patients had pure MIDD, whereas 11 pa tients had LCDD with coexistent myeloma cast nephropathy (LCDD & MCN). Rena l biopsy diagnosis preceded clinical evidence of dysproteinemia in 68% of a ll cases. By immunofluorescence, the composition of deposits included 11 ka ppa /1 lambda (LCDD), 3IgG kappa /2IgG lambda (LHCDD), 5 gamma /1 alpha( (H CDD), and 10 kappa /1 lambda (LCDD & MCN). Patients with pure MIDD presente d with mean serum creatinine of 4.2 mg/dl, nephrotic proteinuria, and hyper tension. Cases of HCDD were associated with a CH1 deletion and frequently h ad hypocomplementemia and a positive hepatitis C virus antibody but negativ e hepatitis C virus PCR. LCDD & MCN is a morphologically and clinically dis tinct entity from pure MIDD, presenting with higher creatinine (mean, 7.8 m g/dl; P = 0.01), greater dialysis dependence (64 versus 26%; P = 0.053), su bnephrotic proteinuria, and less nodular glomerulopathy (18 versus 100%; P < 0.0001). Multiple myeloma was more frequently diagnosed in LCDD & MCN tha n in pure MIDD (91 versus 31%; P = 0.025). Renal and patient survivals were significantly worse in patients with LCDD & MCN (mean, 4 and 22 mo, respec tively), compared with patients with pure MIDD (mean, 22 and 54 mo). Chemot herapy stabilized or improved renal function in 10 of 15 patients (67%) wit h pure MIDD who presented with creatinine of <5.0 mg/dl, emphasizing the im portance of early detection. On multivariate analysis, initial creatinine w as the only predictor of renal and patient survival in pure MIDD, underscor ing the prognostic significance of the renal involvement.