Dysproteinemic kidney diseases occur when B- or plasma cell clones produce pathogenic monoclonal immunoglobulins or light chains that cause kidney damage. The clinical presentation of these disorders ranges from sub–nephrotic-range proteinuria or microscopic hematuria with preserved kidney function to severe nephrotic syndrome to severe acute kidney injury or rapidly progressive glomerulonephritis. These monoclonal immunoglobulins can cause a variety of histologic patterns of injury, including cast nephropathy, glomerular and tubular deposition diseases, amyloidosis, and inflammatory glomerulonephritis.