Hypophosphatemic osteomalacia complicating von Recklinghausen's neurofibromatosis: increase in spinal density on treatment.

A 62-year-old white male with neurofibromatosis presented with multiple fractures and bone pain. He was found to have hypophosphatemic osteomalacia secondary to a renal tubular phosphate leak and was treated with phosphate, 1,25-dihydroxycholecalciferol and calcium. With treatment, his dual photon vertebral bone density increased markedly over 12 months. Repeat iliac crest bone biopsies showed that improvement in bone histology was predominantly cortical. This suggests that dual photon absorptiometry of the spine may be markedly influenced by changes in cortical bone status.