PROFOUND HYPOPHOSPHATEMIA AND ISOLATED HYPERPHOSPHATURIA IN 2 CASES OF MULTIPLE-MYELOMA

We describe the development of severe hypophosphatemia and urinary pho sphate wasting in two patients with multiple myeloma, In both cases, t he serum phosphorus was repeatedly less than 1.0 mg/dL despite vigorou s replacement, and the calculated fractional excretion of urinary phos phorus was greater than 100%, Neither patient demonstrated other tubul ar defects typical of Fanconi's syndrome, With treatment of the myelom a, both patients achieved normalization of the serum phosphorus and no longer required phosphorus supplementation. We believe that multiple myeloma should be considered in the differential diagnosis in patients with profound hypophosphatemia, urinary phosphate wasting, and otherw ise intact tubular function. (C) 1997 by the National Kidney Foundatio n, Inc.