Adult Fanconi syndrome secondary to kappa-light chain myeloma: improvement of tubular functions after treatment for myeloma.

A 66-year-old man with kappa-light chain multiple myeloma had adult Fanconi syndrome. Renal tubular transport abnormalities consisted of renal tubular acidosis, renal glycosuria, aminoaciduria, phosphaturia and renal hypouricemia. After therapy for multiple myeloma, urinary Bence Jones protein became undetectable, and all these renal tubular abnormalities except urate wasting were corrected. Histological examination revealed electron-dense tubular and rod-like deposits in proximal tubular epithelium. This clinical observation suggests that the renal tubular transport defects were secondary to the myeloma process, possibly due to Bence Jones proteinuria.