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Further evidence of affected females with a heterozygous variant in FGF13 causing X-linked developmental and epileptic encephalopathy 90.
Narayanan, DL, Majethia, P, Shrikiran, A, Siddiqui, S, Dalal, A, Shukla, A
European journal of medical genetics. 2022;(1):104403
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Abstract
Developmental and epileptic encephalopathies (DEE) are a genetically heterogeneous group of disorders characterised by early onset epilepsy, epileptiform activity on electroencephalogram and associated developmental delay or neuroregression. With the advent of high throughput sequencing, novel gene-disease associations have been described for DEEs. Voltage activated sodium channels (Nav) regulate neuronal excitability. Fibroblast growth factor homologous factors (FHFs) are proteins, which bind to the C terminal cytoplasmic tails of alpha subunits of Nav channels and influence their function and surface expression. Gain of function hemizygous or heterozygous variants in FGF13 (also known as FHF2) were recently identified as the cause for X-linked developmental and epileptic encephalopathy 90 (DEE90; MIM# 301058) in seven individuals from five families, which included one female. We report an additional female, providing further evidence for a novel de novo heterozygous missense variant in FGF13, NM_004114.5: c.14T > G p.(Ile5Ser) causing X-linked DEE90. In addition, we review the genotype and phenotype of affected individuals with DEE90.
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Phosphaturic Mesenchymal Tumor of Soft Tissue of the Foot: Report of a Case With Review of the Literature.
Bisceglia, M, Galliani, CA, Fraternali Orcioni, G, Perrone, E, Del Giudice, A, Scillitani, A
Advances in anatomic pathology. 2019;(5):320-328
Abstract
Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that ectopically secretes fibroblast growth factor 23, a bone cell-derived protein that regulates phosphate homeostasis. The overproduction of fibroblast growth factor 23 causes a paraneoplastic syndrome characterized by hyperphosphaturia, hypophosphatemia, hypovitaminosis D, and vitamin D refractory rickets/osteomalacia, effects that disappear with tumor removal. The PMT may occur in several anatomic regions, mainly in the limbs, usually involving both soft tissue and bone. Acral locations occur in 10% to 15% of the cases, mostly in the feet, with 95 cases reported in this anatomic region to date. We report a case of a PMT in a young adult male who presented in 2007 with the classic constellation of signs and symptoms. A small soft-tissue tumor was detected in his right heel, 3 years after exhaustively seeking for it by various imaging techniques performed at different institutions. Before the tumor was detected, attempts to manage this patient's osteomalacia with phosphate and vitamin D (both calcitriol and ergocalciferol) supplementation were unsuccessful. Following surgical resection, the patient experienced prompt correction of the phosphaturia and gradual reconstitution of his bone mineralization. The pathologic diagnosis was (benign) PMT, mixed connective tissue type. In 2019, 12 years after resection, the patient is asymptomatic, and his bone mineral homeostasis has been restored.
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Hyperphosphatemic familial tumoral calcinosis secondary to fibroblast growth factor 23 (FGF23) mutation: a report of two affected families and review of the literature.
Chakhtoura, M, Ramnitz, MS, Khoury, N, Nemer, G, Shabb, N, Abchee, A, Berberi, A, Hourani, M, Collins, M, Ichikawa, S, et al
Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA. 2018;(9):1987-2009
Abstract
Hyperphosphatemic familial tumoral calcinosis (HFTC), secondary to fibroblast growth factor 23 (FGF23) gene mutation, is a rare genetic disorder characterized by recurrent calcified masses. We describe young Lebanese cousins presenting with HFTC, based on a retrospective chart review and a prospective case study. In addition, we present a comprehensive review on the topic, based on a literature search conducted in PubMed and Google Scholar, in 2014 and updated in December 2017. While the patients had the same previously reported FGF23 gene mutation (homozygous c.G367T variant in exon 3 leading to a missense mutation), they presented with variable severity and age of disease onset (at 4 years in patient 1 and at 23 years in patient 2). A review of the literature revealed several potential patho-physiologic pathways of HFTC clinical manifestations, some of which may be independent of hyperphosphatemia. Most available treatment options aim at reducing serum phosphate level, by stimulating renal excretion or by inhibiting intestinal absorption. HFTC is a challenging disease. While the available medical treatment has a limited and inconsistent effect on disease symptomatology, surgical resection of calcified masses remains the last resort. Research is needed to determine the safety and efficacy of FGF23 replacement or molecular therapy, targeting the specific genetic aberration. Hyperphosphatemic familial tumoral calcinosis is a rare genetic disorder characterized by recurrent calcified masses, in addition to other visceral, skeletal, and vascular manifestations. It remains a very challenging disease.
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Hyperostosis-hyperphosphatemia syndrome (HHS): report of two cases with a recurrent mutation and review of the literature.
Ghafouri-Fard, S, Abbasi, F, Azizi, F, Javaheri, M, Mehdizadeh, M, Setoodeh, A
Journal of pediatric endocrinology & metabolism : JPEM. 2015;(1-2):231-5
Abstract
Hyperostosis-hyperphosphatemia syndrome (HHS) is a rare autosomal recessive metabolic disorder caused by mutations in the GALNT3 and FGF23 genes. The main features of this disorder include painful swelling of long bones, increased renal reabsorption of phosphate but normal renal function and vitamin D and parathormone levels. Previously, we reported a novel missense mutation in the FGF23 gene in a patient suffering from HHS. In the present report, we demonstrated the same mutation (c.471C>A) in two other cases of HHS with similar clinical manifestations. As this nucleotide change has not been reported previously, it can be a population specific mutation in Iran that can facilitate carrier testing and prenatal diagnosis of HHS.
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Tumor-induced osteomalacia with elevated fibroblast growth factor 23: a case of phosphaturic mesenchymal tumor mixed with connective tissue variants and review of the literature.
Hu, FK, Yuan, F, Jiang, CY, Lv, DW, Mao, BB, Zhang, Q, Yuan, ZQ, Wang, Y
Chinese journal of cancer. 2011;(11):794-804
Abstract
Tumor-induced osteomalacia (TIO), or oncogenic osteomalacia (OOM), is a rare acquired paraneoplastic disease characterized by renal phosphate wasting and hypophosphatemia. Recent evidence shows that tumor-overexpressed fibroblast growth factor 23 (FGF23) is responsible for the hypophosphatemia and osteomalacia. The tumors associated with TIO are usually phosphaturic mesenchymal tumor mixed connective tissue variants (PMTMCT). Surgical removal of the responsible tumors is clinically essential for the treatment of TIO. However, identifying the responsible tumors is often difficult. Here, we report a case of a TIO patient with elevated serum FGF23 levels suffering from bone pain and hypophosphatemia for more than three years. A tumor was finally located in first metacarpal bone by octreotide scintigraphy and she was cured by surgery. After complete excision of the tumor, serum FGF23 levels rapidly decreased, dropping to 54.7% of the preoperative level one hour after surgery and eventually to a little below normal. The patient's serum phosphate level rapidly improved and returned to normal level in four days. Accordingly, her clinical symptoms were greatly improved within one month after surgery. There was no sign of tumor recurrence during an 18-month period of follow-up. According to pathology, the tumor was originally diagnosed as "lomangioma" based upon a biopsy sample, "proliferative giant cell tumor of tendon sheath" based upon sections of tumor, and finally diagnosed as PMTMCT by consultation one year after surgery. In conclusion, although an extremely rare disease, clinicians and pathologists should be aware of the existence of TIO and PMTMCT, respectively.
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Persistent tumor-induced osteomalacia confirmed by elevated postoperative levels of serum fibroblast growth factor-23 and 5-year follow-up of bone density changes.
Zimering, MB, Caldarella, FA, White, KE, Econs, MJ
Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists. 2005;(2):108-14
Abstract
OBJECTIVE To describe a case of persistent tumor-induced osteomalacia, determine whether serum fibroblast growth factor-23 (FGF-23) levels postoperatively indicate incomplete tumor resection, and report lumbar spine and forearm bone mineral density (BMD) changes during 5 years of follow-up. METHODS We present clinical, radiologic, histologic, and bone densitometry data as well as serum FGF-23 levels (determined with use of a novel C-terminal enzyme-linked immunosorbent assay) from the study patient and discuss these findings in the context of previous literature. RESULTS A 52-year-old man, who presented with muscle weakness and multiple fractures, was found to have low values for serum phosphorus, serum 1,25-dihydroxyvitamin D, and maximal tubular reabsorption of phosphate per glomerular filtration rate, a high level of serum alkaline phosphatase, and a normal serum concentration of parathyroid hormone, characteristic of tumor-induced osteomalacia. Magnetic resonance imaging to evaluate an abnormality of the left foot revealed a soft tissue mass, biopsy of which confirmed the presence of a benign, phosphaturic, mesenchymal tumor. The baseline serum FGF-23 level (2,050 RU/mL) was more than 17 times the upper limit of normal for adults (23 to 118 RU/mL) and decreased substantially within 1 day after partial resection of the tumor but remained above normal postoperatively. BMD changes indicated rapid substantial recovery of vertebral BMD but ongoing loss of forearm bone density. CONCLUSION The serum FGF-23 level is high in a substantial proportion of patients with tumor-induced osteomalacia. The postoperative above normal levels of serum FGF-23 correlated with known persistence of tumor in our study patient. In a patient with normal renal function, such as our study patient, levels of serum FGF-23 studied with use of the C-terminal enzyme-linked immunosorbent assay reached their nadir within 24 hours postoperatively. This result suggests that this assay can provide clinicians with rapid prognostic information in patients with known or suspected residual tumor. BMD should be assessed at both appendicular and axial sites in patients with persistent tumor-induced osteomalacia.