Martini, Giuseppe and Valleggi, Fabrizio and Gennari, Luigi and Merlotti, Daniela and De Paola, Vincenzo and Valenti, Roberto and Nuti, Ranuccio
(2006)
Oncogenic osteomalacia.
Clinical cases in mineral and bone metabolism, 3 (1).
pp. 76-83.
ISSN 1724-8914
Abstract
Tumor-induced osteomalacia (TIO) is a rare paraneoplastic
syndrome characterized biochemically by hypophosphatemia,
excessive urinary phosphate excretion, low 1,25-dihydroxyvitamin D levels, and clinically by osteomalacia, pseudofractures, bone pain, fatigue, and muscle weakness. TIO can occur in patients with a variety of benign mesenchimal tumors
(hemangiopericitomas, fibromas, angiosarcomas, etc.) and
the disease is invariably curable with the removal of the tumor, indicating that it has humoral basis. Phosphate wasting
and the defect in vitamin D synthesis are caused by a humoral
factor produced by tumors, initially termed phosphatonin, and
recently identified as fibroblast growth factor-23 (FGF-23) although other substances as secreted frizzled-related protein 4
(SFRP4) and matrix extracellular phospho-glycoprotein
(MEPE) can be involved in pathophysiology of osteomalacia.
In contrast with more common forms of osteomalacia, patients with TIO have normal serum calcium, normal serum 25-
hydroxy-vitamin D and normal intact serum parathyroid hormone. On the other hand TIO is biochemically indistinguishable from several inherited forms of hypophosphatemic rickets as X-linked hypophosphatemia (XLH) and autosomical
dominant hypophosphatemic rickets (ADHR). The definitive
diagnosis of TIO is established by identification of the
causative tumor and remission of the syndrome after complete tumor resection. Recently a few cases in which 111In-pentetreotide scintigraphy visualized the tumor have been reported and also positron emission tomography using F-18-fluorodeoxyglucose showed encouraging results. When the suspected tumour cannot be located, periodical follow-up with
conventional imaging is indicated with special attention directed to craniofacial locations and extremities because they
are the more common localization for tumour. In conclusion in
patients with TIO resection of a tumour is the treatment of
choice; if the tumour cannot be found or if the tumour is unresectable for its location, chronic administration of phosphate
and calcitriol is indicated.
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Oncogenic osteomalacia. (deposited 23 Jan 2014 14:36)
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