Heavy chain amyloidosis and heavy chain deposition disease are the only known kidney diseases caused by the deposition of truncated immunoglobulin heavy chains. Fibrillary glomerulonephritis typically results from deposition of DNAJB9 (DnaJ heat shock protein family [Hsp40] member B9) and polytypic immunoglobulin G (IgG). We describe a patient with monoclonal gammopathy (IgG with λ light chain) who developed DNAJB9-negative fibrillary glomerulonephritis leading to end-stage kidney disease, with recurrence in 2 kidney allografts.