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Myeloma and the Kidney Ryan Sanford 2.22.2010 How Often is the Kidney Involved Symptomatic MM: CRAB hyperCalcemia Renal dysfunction Anemia Bone lesions 1/5 to 2/5 patients with MM have renal involvement What Does it Signify? At presentation SCr 1.5 ? 80% alive at 1 year SCr 2.3 ? 50% alive at 1 year Renal Improvement to MM Treatment also favorable The Immunoglobulin Light Chains come in lambda and kappa A Few General Points First The Proteins of MM Light chains (LC) almost always the problem Various potential proteins to be produced Intact immunoglobulins +/- Light Chains and Heavy Chains The SPEP: Not a good test to identify LCs Increased sensitivity if coupled with serum immunofixation Can only quantify LCs with direct assessment The UPEP Prior to serum free light chain assessment, the UPEP was the test of choice to find LCs The Light Chain (LC) aka Bence Jones proteins Monoclonal A ratio of κ:λ Freely filtered, absorbed in PCT The LC biochemical properties determines the type, if any, of renal disease The Serum Free Light Chain Assessment Polyclonal ABs directed at hidden LC epitopes (when a full Ig) used for sensitive quantification of κ and λ light chains Coupled with SPEP more Sn/Sp than SPEP/UPEP Could be replacing UPEP as test of choice What Types of Involvement Light chain cast nephropathy – Myeloma Kidney [40% of cases] Light chain deposition disease [10%] Primary AL Amyloidosis [10%] Also: Hypercalcemia, interstitial nephritis, acquired Fanconi’s syndrome, GN Proteinuria in MM Albuminuria [a grossly positive U/a for protein] If positive: Nonspecfic glomerular leak, nephrosis LCDD or Amyloidosis If negative: other proteins or no protein in urine; cast nephropathy Addition of Sulfosalicylic Acid to Supernatant If bland sediment and minimal protein on U/a Precipitates all urinary protein If positive suggestive of light chains in urine Cast Nephropathy / Myeloma Kidney Acute or Chronic Worsened by volume depletion Two mechanisms Intratubular cast