Hypophosphatemic osteomalacia in von Recklinghausen neurofibromatosis.

Skeletal lesions are not uncommon in von Recklinghausen neurofibromatosis. Most of them are considered to be dysplastic in nature. Association of osteomalacia or rickets with neurofibromatosis has been documented only rarely. Reported herein is a 40-year-old woman with known von Recklinghausen neurofibromatosis who presented with bone pain, multiple pseudofractures, marked increase in osteoid by bone biopsy, and hypophosphatemia with renal phosphate wasting. Treatment with oral phosphate and vitamin D was effective. A survey of the literature revealed that 34 similar cases have been reported in the past. Although the exact pathogenetic mechanism remains to be determined, osteomalacia in neurofibromatosis appears to be distinct from more common dysplastic skeletal affections of this disease, being characterized by later onset in adulthood as a rule, renal phosphate loss with hypophosphatemia, multiple pseudofractures in typical cases, and response to treatment with pharmacological dose of vitamin D with or without phosphate supplement.