[Non-rachitic hypophosphatemic osteopathy].

We have identified a patient with a condition called Hypophosphatemic Bone Disease (HBD). This disorder of phosphate metabolism is unrecorded by Dent in his final classification of metabolic bone diseases and has been described by Scriver C.R. and coll. Although the condition is in same ways analogous to X-Linked Hyophosphatemia (XLH), there are important differences between the two diseases. For example, there is selective impairment in the tubular reabsorption of phosphate in HBD but the defect is less severe and it is clearly different from that described in XLH. Clinical manifestations of HBD appear in infancy, but the dwarfism and the bone changes are less severe than in XLH at comparable concentrations of plasmatic phosphorus in the two diseases. While in both conditions there is osteomalacia of endostal trabecular bone, only in XLH is florid rickets present, affecting the epiphyses and compromising linear growth. The phosphaturic response to PTH infusion is abnormal in qualitative aspects, but it is present in HBD, and this differs considerably from that described in XLH. The treatment with oral load of phosphates and 1,25(OH)2D3 in every patient with HBD, and so in our patient, is accompanied by increase in serum phosphorus, with improved tubular reabsorption of phosphate anion and a fall of hydrossiprolinuria with bone healing; this combination of responses is not present in XLH.