ABSTRACT
The case here reported of 72 year-old female with osteomalacia in whom an adult's Fanconi's syndrome with distal tubular involvement and a monoclonal IgG-lambda paraprotein were discovered. There was urinary excretion of lambda light chains without evidence of myeloma or amyloidosis. Such apparently unrelated entities might be subject to an unitary pathophysiological approach: the nephrotoxicity of light chains could cause a Fanconi's syndrome, which in turn would give rise to osteomalacia through phosphate depletion. It is noteworthy that in this patient the urinary excretion of light chains was of the lambda type, in contrast to similar cases described in the literature which presented mostly kappa chains. The likelihood of this patient developing myeloma or amyloidosis at a later stage is discussed.
