Une fracture pathologique de la hanche chez un adulte révélant une ostéomalacie hypophosphorémique oncogénique secondaire à une dysplasie fibreuse des os.

Abstract

Oncogenic hypophosphatemic osteomalacia is a rare acquired condition (about 160 reported cases). The initial abnormality is the unregulated secretion of FGF-23 by small growth mesenchymal tumors. Fibrous dysplasia is a well-known cause of oncogenic osteomalacia, with the polyostotic form complicated in 50% of cases with severe hypophosphatemia. We report here the case of a 43 years-old man, admitted for diffuses bone pain and muscular proximal weakness, evolving for 2 years, complicated with a pathological femoral neck fracture. Lab studies found severe hypophosphatemia and an elevation of alkaline phosphatases with normal levels of serum calcium, 25OH-vit D3 and PTH. X-Rays revealed a diffuse bone demineralization with multiple vertebral fractures and a fracture of the femoral neck associated with multiple lytic lesions of the femoral diaphysis. Histological examination has concluded fibrous dysplasia. Main etiologies, such as iatrogenic causes and Fanconi syndrome, have not been considered. Treatment with phosphorus associated with 1,25OH-Vit D3 has been installed, associated with intravenous infusions of bisphosphonates.