Lambda-light-chain nephropathy with Fanconi's syndrome.

Renal disease is a common complication of paraproteinemia, but light-chain nephropathy with resultant Fanconi's syndrome is unusual. In a 60-year-old man with Fanconi's syndrome, the underlying disease was a well-differentiated lymphocytic lymphoma, with two paraproteins and lambda-light-chain proteinuria. A renal biopsy specimen showed crystals in tubular cells, more prominent in proximal than distal tubules. Immunoperoxidase studies confirmed the lambda-light-chain content of the crystals. All previous cases studied by biopsy have involved kappa light chains. Light chains are thought to be toxic to the tubular epithelium, resulting in Fanconi's syndrome. Case reports of lymphoproliferative disorders associated with paraproteinemia and Fanconi's syndrome suggest a somewhat better prognosis with this clinical entity.