1. ¹Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
2. ²Division of Hematology, Mayo Clinic, Rochester, Minnesota, USA
3. ³Department of Laboratory Medicine and Pathology, Division of Transfusion Medicine, Mayo Clinic, Rochester, Minnesota, USA

Correspondence: N Leung, Division of Nephrology and Hypertension, 200 First Street SW, Mayo Clinic Rochester, MN 55905, USA. E-mail: leung.nelson@mayo.edu

Received 11 October 2007; Revised 14 January 2008; Accepted 22 January 2008; Published online 2 April 2008.

Abstract

Cast nephropathy is the most common cause of renal disease in multiple myeloma, however, treatment with plasma exchange remains controversial even after 3 randomized controlled studies. We sought to determine the importance of diagnostic confirmation and goal directed therapy in the treatment of cast nephropathy in forty patients with confirmed multiple myeloma and renal failure who underwent plasma exchange. A positive renal response was defined as a decrease by half in the presenting serum creatinine and dialysis independence. No baseline differences were noted between eventual renal responders and non-responders. Three quarters of the patients with biopsy proven cast nephropathy resolved their renal disease when the free light chains present in the serum were reduced by half or more but there was no significant response when the reduction was less. The median time to a response was about 2 months. In patients without cast nephropathy, renal recovery occurred despite reductions in free light chain levels of the serum. No association was found between free light chains in the serum, urinary monoclonal proteins, overall proteinuria and cast nephropathy. We found that the relationship between renal recovery and free light chain reduction was present only in patients with biopsy proven cast nephropathy showing the importance of extracorporeal light chain removal in this disease.