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Other bone diseases in the elderly
Published in Charles M Court-Brown, Margaret M McQueen, Marc F Swiontkowski, David Ring, Susan M Friedman, Andrew D Duckworth, Musculoskeletal Trauma in the Elderly, 2016
Patients with hypophosphataemic osteomalacia and osteomalacia associated with chronic renal impairment require treatment with active vitamin D metabolites – either 1-alpha-hydroxyvitamin D or 1,25 dihydroxyvitamin D in doses of 1–3 micrograms daily. Patients with tumour induced osteomalacia may also require phosphate supplements.
The Nature of Renal Function
Published in Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George, The Scientific Basis of Urology, 2010
The activity of NPT IIa is inhibited by not only PTH, but also a recently described protein of the fibroblast growth factor family, FGF23(73), produced in osteocytes. FGF23 is also secreted by some tumors that cause tumor-induced osteomalacia, a paraneoplastic syndrome leading to renal phosphate wasting, hypophosphatemia, and rickets/osteomalacia (74). FGF23 is inactivated by a yet unidentified peptidase that cleaves it into two inactive fragments. Mutations in FGF23 that render it resistant to enzymatic cleavage but do not inhibit its activity cause a rare, autosomal dominant, form of hypophosphatemic rickets (75). Two other proteins are also expressed in osteocytes, and are believed to be involved in the regulation of expression of the gene for FGF23. The gene for the first of these to be described is called PHEX (a phosphate-regulating gene with homologies to genes for endopeptidases on the X chromosome), and is mutated in patients with the relatively common X-linked hypo-phosphatemic rickets (76). The second is called DMP-1 (dentin matrix protein-1) and the gene for it is mutated in the very rare autosomal recessive hypophosphatemic rickets (77). The phenotypes of all these forms of hereditary hypophosphatemia are similar, and are caused by inhibition of NPT IIa either by the uncontrolled release of FGF23 or by failure of its enzymatic degradation, leading to inhibition of P reabsorption by NPT IIa, phosphaturia, and hypophosphatemic rickets. Yet another gene, rather quaintly called klotho in honor of the Greek goddess who spins the thread of life, is mutated in transgenic mice with a premature aging syndrome. Further studies have shown that klotho is expressed in the renal tubule and is an essential coreceptor for FGF23. Klotho-deficient mice and FGF-deficient mice develop identical phenotypes, indicating that klotho expression in the renal tubules is necessary for the renal effect of FGF23. These interrelationships are reviewed at greater length by Kurosu and Kuro-o (78).
Osteomyelitis and pyomyositis due to Staphylococcus aureus in an osteomalacic adult with multiple fractures
Published in Journal of Community Hospital Internal Medicine Perspectives, 2021
Masumi Ogawa, Takatoshi Kitazawa, Yusuke Yoshino, Koji Morita, Toshio Ishikawa, Yasuo Ota
In this patient, the cause of his multiple fractures was believed to be FGF23-related hypophosphatemic osteomalacia. Moreover, his bone strength was probably impaired by secondary hyperparathyroidism, which was presumably due to 25-hydroxyvitamin D deficiency, renal dysfunction, and FGF23-induced inhibition of 1α, 25-dihydroxyvitamin D synthesis. FGF23 measurement had been reported to be useful for the differential diagnosis of hypophosphatemic diseases, such as tumor-induced osteomalacia [15]. One of the common clinical manifestation in osteomalacic patients is fracture, which is observed in 76% [16]. Curiously, for some reason, our patient had mild tenderness on some fracture sites, despite his normal sensory function. We speculated that the external force on the ribs might not have been strong.
Tumor-induced osteomalacia caused by a massive phosphaturic mesenchymal tumor of the acetabulum: A case report
Published in Modern Rheumatology, 2018
Kimitaka Nakamura, Masanobu Ohishi, Tomoya Matsunobu, Yasuharu Nakashima, Akio Sakamoto, Akira Maekawa, Yoshinao Oda, Yukihide Iwamoto
Tumor-induced osteomalacia (TIO) is a rare metabolic bone disease that is caused by tumors producing fibroblast growth factor 23 (FGF-23). Overproduction of FGF-23 by the tumors induces hypophosphatemia and 1,25(OH)2 vitamin D3 deficiency, which results in defects in the mineralization of newly formed bone collagen [1]. The patients experience bone pain, proximal muscle weakness, osteopenia, and multiple bone fractures [1]. The excision of the tumors can abrogate these symptoms. However, owing to a lack of knowledge concerning the existence of the disease, the period between the onset of symptoms to diagnosis is often long. The responsible tumors in the majority of cases are phosphaturic mesenchymal tumors (PMT). PMTs are usually very small in size and are often difficult to locate [1]. Herein, we report a case of TIO caused by a large PMT that was destroying the acetabulum.
Treatment of fibrous dysplasia: focus on denosumab
Published in Expert Opinion on Biological Therapy, 2022
Bogdan Huzum, Sabina Antoniu, Raluca Dragomir
Burosumab is a monoclonal antibody targeting FGF-23. It has been approved in the United States for the treatment of X-linked hypophosphatemia and for tumor-induced osteomalacia [45]. Given that FD hypophosphatemia is also a pathogenic feature and is the result of increased renal excretion, burosumab might represent a potential therapeutic agent that might successfully address the limitations of vitamin D and phosphorus supplementation, which are hypercalciuria and gastrointestinal intolerance [46]. Case reports on the use of burosumab in FD are being published. Larger case series are expected to be reported in the near future. One case report described a 7-year-old boy with severe FD/MAS diagnosed during the first year of life. The hypophosphatemia was initially responsive to phosphate supplementation and calcitriol, but with rapid development of feeding problems and subsequent bilateral nephrocalcinosis and hypercalciuria. He had bone involvement throughout his body and developed 17 fractures and various deformities as sequelae, beginning at the age of 7 years. At the age of 4 years, he received a bisphosphonate infusion. This resulted in Fanconi syndrome. The next dose was stopped. Burosumab was administered after detection of elevated serum FGF-23 levels. A 20-mg dose was administered every 2 weeks for 17 months. This regimen decrease pain and improved functional status after the first dose. Bone imaging did not detect baseline abnormalities, and no adverse events were evident [47]. Further studies are needed to evaluate the efficacy and safety of burosumab. It is worth mentioning that this therapy is not able or has not yet been demonstrated as being influential for abnormally increased osteoclastogenesis. Thus, the therapy might be reserved for the pathogenic treatment of FD/MAS ‘satellite’ abnormalities, such as hypophosphatemia.