Proliferative glomerulonephritis due to monoclonal deposition with organized substructures

A growing number of monoclonal gammopathy-associated kidney diseases recently have been recognized. We present the case of a 54-year-old man who presented with acute kidney injury and hypocomplementemia. Kidney biopsy confirmed the presence of immunoglobulin G κ pseudothrombi with intracytoplasmic crystals in glomeruli and tubules. Levels of κ free light chains were elevated without a detectable monoclonal gammopathy, and bone marrow biopsy results were normal. After the first course of rituximab, cyclophosphamide, and dexamethasone in addition to daily plasmapheresis, kidney function recovered within 2 weeks and dialysis therapy was discontinued. Treatment for monoclonal protein-induced kidney disease should be considered in the setting of progressive decreased kidney function, even in the absence of a circulating monoclonal protein or cellular clone of origin.