Hypercalciuria secondary to chronic hypophosphatemia

Abstract

A 41-year-old man presented with back pain, osteoporosis and vertebral crushing. Laboratory studies revealed persistent hypophosphatemia, normocalcemia and elevated levels of 1,25-dihydroxy-vitamin D. Other mineral metabolism tests showed a low tubular maximal phosphate reabsorption per glomerular filtrate, an absorptive hypercalciuria and a normal intestinal absorption of phosphate. Hyperparathyroidism was ruled out by an intravenous calcium loading test. Bone histopathology was consistent with osteomalacia. Treatment with phosphate supplements resulted in resolution of symptoms and normalization of laboratory parameters. To our knowledge, this can be a sporadic form of a disorder recently described: hereditary hypophosphatemic rickets with hypercalciuria.