X-linked hypophosphataemia (XLH) is due to mutations in phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and represents the most common heritable form of rickets. In this condition, the hormone fibroblast growth factor 23 (FGF23) is produced in excessive amounts for still unknown reasons, and causes renal phosphate wasting and suppression of 1,25-dihydroxyvitamin D, leading to low serum phosphate concentrations. Prolonged hypophosphataemia decreases apoptosis of hypertrophic chondrocytes in growth plates (causing rickets) and decreases mineralisation of existing bone (causing osteomalacia). In contrast to historical conventional treatment with oral phosphate supplements and active vitamin D for the last 50 years, the new anti-FGF23 antibody treatment (burosumab) targets the primary pathology by blocking FGF23, thereby restoring phosphate homeostasis. In this review, we describe the changes in treatment monitoring, treatment targets and long-term treatment goals, including future opportunities and challenges in the treatment of XLH in children.
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http://dx.doi.org/10.1007/s40272-020-00381-8 | DOI Listing |
Front Endocrinol (Lausanne)
January 2025
Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
Tertiary hyperparathyroidism is characterized by hypercalcemia resulting from autonomous parathyroid hormone production and usually occurs after a prolonged period of secondary hyperparathyroidism. This condition can be a complication of X-linked hypophosphatemia (XLH), a rare genetic disease characterized by renal phosphate loss and consequent hypophosphatemia. Parathyroidectomy is considered the first-line therapy but surgical intervention can be complicated by hungry bone syndrome.
View Article and Find Full Text PDFNat Rev Nephrol
January 2025
APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, endo ERN and ERN BOND, Paris, France.
X-linked hypophosphataemia (XLH) is a rare metabolic bone disorder caused by pathogenic variants in the PHEX gene, which is predominantly expressed in osteoblasts, osteocytes and odontoblasts. XLH is characterized by increased synthesis of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23), which results in renal phosphate wasting with consecutive hypophosphataemia, rickets, osteomalacia, disproportionate short stature, oral manifestations, pseudofractures, craniosynostosis, enthesopathies and osteoarthritis. Patients with XLH should be provided with multidisciplinary care organized by a metabolic bone expert.
View Article and Find Full Text PDFBMJ Case Rep
January 2025
Pediatrics, Lokmanya Tilak Municipal General Hospital and Lokmanya Tilak Municipal Medical College, Mumbai, Maharashtra, India.
Rickets in children usually present with skeletal manifestations. However, they can also rarely present with extraskeletal manifestations, one of them being respiratory insufficiency. We present an unusual case of a girl in early childhood with respiratory insufficiency, which turned out to be due to the underlying vitamin D-dependent rickets (VDDR).
View Article and Find Full Text PDFCalcif Tissue Int
January 2025
Department of Paediatric Endocrinology, Alder Hey Children's Hospital, Liverpool, UK.
Autosomal recessive hypophosphatemic rickets type 2 (ARHR2) is an uncommon hereditary form of rickets characterised by chronic renal phosphate loss and impaired bone mineralisation. This results from compound heterozygous or homozygous pathogenic variants in ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), a key producer of extracellular inorganic pyrophosphate (PPi) and an inhibitor of fibroblast growth factor23 (FGF23). ENPP1 deficiency impacts FGF23 and increases its activity.
View Article and Find Full Text PDFBMC Mol Cell Biol
January 2025
Department of Stomatology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, 150001, China.
Background: Inactivation or mutations of FAM20C causes human Raine Syndrome, which manifests as lethal osteosclerosis bone dysplasia or non-lethal hypophosphatemia rickets. However, it is only hypophosphatemia rickets that was reported in the mice with Fam20c deletion or mutations. To further investigate the local and global impacts of Fam20c mutation, we constructed a knock-in allele carrying Fam20c mutation (D446N) found in the non-lethal Raine Syndrome.
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