Severe muscle weakness secondary to paraneoplastic hypophosphatemia in neuroblastoma.

We report a 28-year-old woman who presented with severe proximal muscle weakness secondary to paraneoplastic hypophosphatemia and associated with recurrent neuroblastoma. The biochemical findings included hyperphosphaturia, a reduced serum level of 1,25-dihydroxyvitamin-D3, elevated alkaline phosphatase and normocalcemia which are pathognomic for paraneoplastic hypophosphatemia. Following systemic chemotherapy and supplementation of 1,25-dihydroxyvitamin-D3 a complete remission of the neuroblastoma was achieved and all features of the paraneoplastic hypophosphatemia gradually disappeared. In the differential diagnosis of muscle weakness, hypophosphatemia should be included. Paraneoplastic hypophosphatemia associated with metastatic neuroblastoma has not been reported previously. Diagnosis, mechanism and therapy of paraneoplastic hypophosphatemia are shortly reviewed.