Long-term prognosis of monoclonal immunoglobulin-associated glomerular diseases with non-organized deposits: A report of 38 cases from a Japanese single center

Monoclonal immunoglobulin (MIg)-associated glomerular diseases with non-organized deposits are rare disorders. They have recently been categorized into light chain deposit disease (LCDD), light and heavy chain deposit disease (LHCDD), heavy chain deposit disease (HCDD), proliferative glomerulonephritis with MIg deposits (PGNMID) and its light chain only variant (PGNMID-LC), and membranous glomerulopathy with light chain-restricted deposits (MG-LC). In our Japanese cohort of more than 9,500 patients who underwent renal biopsy (1979 - 2020), we evaluated clinicopathological features and long-term outcomes in 38 patients with MIg-associated glomerular diseases with non-organized deposits: LCDD (n = 9), LHCDD (n = 8), HCDD (n = 5), PGNMID-membranoproliferative glomerulonephritis (MPGN) (n = 7), PGNMID-LC (n = 2), and MG-LC (n = 7). In patients with LCDD, a low estimated glomerular filtration rate (eGFR) at biopsy, a high detection rate of urinary MIgs, a high incidence rate of multiple myeloma, and sever tubulointerstitial and vascular lesions were significant clinicopathological characteristics. Median duration of follow-up in each group was 42 - 114 months. Most patients were treated with steroid-based therapy. Patients with LCDD, LHCDD, HCDD, and MG-LC were recently treated with bortezomib-based therapy. Renal survival rate was significantly shorter for LCDD than of PGNMID and MG-LC. Patient survival rate was significantly longer for MG-LC than HCDD and PGNMID. Major causes of death were pulmonary and cardiovascular complications. Among disease groups, significant differences were observed in eGFR at biopsy, detection rates of urinary MIgs, incidence rates of multiple myeloma, severities of tubulointerstitial and vascular lesions, and long-term outcomes.