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Giannini S, Bianchi ML, Rendina D, Massoletti P, Lazzerini D, Brandi ML. Burden of disease and clinical targets in adult patients with X-linked hypophosphatemia. A comprehensive review. Osteoporos Int 2021; 32:1937-1949. [PMID: 34009447 PMCID: PMC8510985 DOI: 10.1007/s00198-021-05997-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 05/06/2021] [Indexed: 11/17/2022]
Abstract
UNLABELLED X-linked hypophosphataemia (XLH) is a lifelong condition. Despite the mounting clinical evidence highlighting the long-term multi-organ sequelae of chronic phosphate wasting and consequent hypophosphatemia over the lifetime and the morbidities associated with adult age, XLH is still perceived as a paediatric disease. INTRODUCTION Children who have XLH need to transition from paediatric to adult healthcare as young adults. While there is general agreement that all affected children should be treated (if the administration and tolerability of therapy can be adequately monitored), there is a lack of consensus regarding therapy in adults. METHODS To provide guidance in both diagnosis and treatment of adult XLH patients and promote better provision of care for this potentially underserved group of patients, we review the available clinical evidence and discuss the current challenges underlying the transition from childhood to adulthood care to develop appropriate management and follow-up patterns in adult XLH patients. RESULTS AND CONCLUSIONS Such a multi-systemic lifelong disease would demand that the multidisciplinary approach, successfully experienced in children, could be transitioned to adulthood care with an integration of specialized sub-disciplines to efficiently control musculoskeletal symptoms while optimizing patients' QoL. Overall, it would be desirable that transition to adulthood care could be a responsibility shared by the paediatric and adult XLH teams. Pharmacological management should require an adequate balance between the benefits derived from the treatment itself with complicated and long-term monitoring and the potential risks, as they may differ across age strata.
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Affiliation(s)
- S Giannini
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy.
| | - M L Bianchi
- Experimental Laboratory for Children's Bone Metabolism Research, Bone Metabolism Unit, Istituto Auxologico Italiano IRCCS, Milano, Italy
| | - D Rendina
- Department of Clinical Medicine and Surgery, Federico II University, Napoli, Italy
| | - P Massoletti
- Medical Affairs, Kyowa Kyrin, Basiglio, (MI), Italy
| | - D Lazzerini
- Medical Affairs, Kyowa Kyrin, Basiglio, (MI), Italy
| | - M L Brandi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Firenze, Firenze, Italy
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Papadopoulou A, Bountouvi E, Karachaliou FE. The Molecular Basis of Calcium and Phosphorus Inherited Metabolic Disorders. Genes (Basel) 2021; 12:genes12050734. [PMID: 34068220 PMCID: PMC8153134 DOI: 10.3390/genes12050734] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 02/07/2023] Open
Abstract
Calcium (Ca) and Phosphorus (P) hold a leading part in many skeletal and extra-skeletal biological processes. Their tight normal range in serum mirrors their critical role in human well-being. The signalling “voyage” starts at Calcium Sensing Receptor (CaSR) localized on the surface of the parathyroid glands, which captures the “oscillations” of extracellular ionized Ca and transfers the signal downstream. Parathyroid hormone (PTH), Vitamin D, Fibroblast Growth Factor (FGF23) and other receptors or ion-transporters, work synergistically and establish a highly regulated signalling circuit between the bone, kidneys, and intestine to ensure the maintenance of Ca and P homeostasis. Any deviation from this well-orchestrated scheme may result in mild or severe pathologies expressed by biochemical and/or clinical features. Inherited disorders of Ca and P metabolism are rare. However, delayed diagnosis or misdiagnosis may cost patient’s quality of life or even life expectancy. Unravelling the thread of the molecular pathways involving Ca and P signaling, we can better understand the link between genetic alterations and biochemical and/or clinical phenotypes and help in diagnosis and early therapeutic intervention.
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Delayed Diagnosis, Difficult Decisions: Novel Gene Deletion Causing X-Linked Hypophosphatemia in a Middle-Aged Man with Achondroplastic Features and Tertiary Hyperparathyroidism. Case Rep Endocrinol 2021; 2021:9944552. [PMID: 33953992 PMCID: PMC8064789 DOI: 10.1155/2021/9944552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 03/16/2021] [Accepted: 04/06/2021] [Indexed: 11/17/2022] Open
Abstract
X-linked hypophosphatemia (XLH) is the most prevalent form of hereditary hypophosphatemic rickets associated with phosphate wasting. However, its diagnosis is often missed, resulting in patients presenting late in the course of the disease when complications such as tertiary hyperparathyroidism and renal failure have already set in. Phosphate and calcitriol replacement, both of which have undesirable consequences of their own, have historically been the main stay of therapy. We describe the case of a 57-year-old gentleman with tertiary hyperparathyroidism, who was mislabelled as having achondroplasia for many years before we made a diagnosis of XLH in him. His XLH was found to be due to a hereto unreported deletion of entire exon 14 with partial deletions of introns 13 and 14 of the PHEX gene. Perioperative management in him was fraught with surgical and medical difficulties including an operation that was technically complicated due to his multiple anatomical deformities. Our case also highlights the critical importance of timely recognition and accurate diagnosis of XLH, as well as the long-term multidisciplinary management that is needed for this disorder.
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Diagnosis and management of X-linked hypophosphatemia in children and adolescent in the Gulf Cooperation Council countries. Arch Osteoporos 2021; 16:52. [PMID: 33660084 PMCID: PMC7929956 DOI: 10.1007/s11657-021-00879-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 01/04/2021] [Indexed: 02/03/2023]
Abstract
INTRODUCTION X-linked hypophosphatemia (XLH) is a rare inherited cause of hypophosphatemic rickets and osteomalacia. It is caused by mutations in the phosphate-regulating endopeptidase homolog, X-linked (PHEX). This results in increased plasma fibroblast growth factor-23 (FGF23), which leads to loss of renal sodium-phosphate co-transporter expression leading to chronic renal phosphate excretion. It also leads to low serum 1,25-dihydroxyvitamin D (1,25(OH)2D), resulting in impaired intestinal phosphate absorption. Chronic hypophosphatemia in XLH leads to impaired endochondral mineralization of the growth plates of long bones with bony deformities. XLH in children and adolescents also causes impaired growth, myopathy, bone pain, and dental abscesses. XLH is the most frequent inherited cause of phosphopenic rickets/osteomalacia. Hypophosphatemia is also found in calcipenic rickets/osteomalacia as a result of secondary hyperparathyroidism. Thus, chronic hypophosphatemia is a common etiologic factor in all types of rickets. RESULTS There is considerable overlap between symptoms and signs of phosphopenic and calcipenic rickets/osteomalacia. Wrong diagnosis leads to inappropriate treatment of rickets/osteomalacia. Nutritional rickets and osteomalacia are common in the Gulf Cooperation Council countries which include Saudi Arabia, United Arab Emirates, Kuwait, Qatar, Bahrain, and Oman. Due to high levels of consanguinity in the region, genetic causes of phosphopenic and calcipenic rickets/osteomalacia are also common. CONCLUSION This guideline was developed to provide an approach to the diagnosis of XLH, especially where there is no family history of the disease, and that other related conditions are not mistaken for XLH. We also guide the medical management of XLH with conventional treatment and with burosumab, a recombinant human IgG1 monoclonal antibody to FGF23.
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Seefried L, Smyth M, Keen R, Harvengt P. Burden of disease associated with X-linked hypophosphataemia in adults: a systematic literature review. Osteoporos Int 2021; 32:7-22. [PMID: 32710160 PMCID: PMC7755619 DOI: 10.1007/s00198-020-05548-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 07/08/2020] [Indexed: 12/30/2022]
Abstract
UNLABELLED This systematic review collated evidence on the burden of XLH in adults. Data captured highlight the substantial ongoing burden of XLH in adulthood and identified unmet needs. Greater awareness and understanding of the impact of XLH in adulthood are needed to improve care and outcomes in adults with XLH. INTRODUCTION X-linked hypophosphataemia (XLH) is a rare metabolic bone disease characterized by renal phosphate wasting and musculoskeletal manifestations. Whilst the disease's impact in children is well documented, information on the effects of this progressive, debilitating condition on adults is lacking. This systematic review aimed to collate existing evidence on the burden of XLH in adulthood to identify unmet needs. METHODS MEDLINE, Embase and Cochrane Library databases and recent congress reports were searched on 19 February 2019 for English-language publications describing the medical, humanistic and socio-economic impact of XLH in adults (≥ 18 years old). In addition, a structured Internet search was conducted. RESULTS Of the 2351 articles identified, 91 met the selection criteria along with 44 congress abstracts. Data show that adults with XLH experience a range of clinical manifestations, particularly skeletal deformities and (pseudo)fractures, along with pain, dental abnormalities and impaired physical function and mobility. XLH in adulthood impacts on quality of life and places limitations on daily activities. The level of healthcare resource utilization among adults with XLH is indicative of substantial socio-economic burden; further research is needed to quantitate the economic impact on the healthcare system, society and patients. Adults with XLH may not receive appropriate care and treatment; a possible explanation for this is a lack of awareness among healthcare professionals. CONCLUSION XLH in adults is associated with considerable disease burden and unmet needs. Forthcoming studies and increased awareness of the impact of XLH in adulthood should help to improve management of XLH in adulthood and patient outcomes.
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Affiliation(s)
- L Seefried
- Orthopedic Institute, König-Ludwig Haus, University of Würzburg, Würzburg, Germany
| | - M Smyth
- Kyowa Kirin International, Galashiels, UK
| | - R Keen
- Royal National Orthopaedic Hospital, Stanmore, UK
| | - P Harvengt
- RVRH-XLH, French association of patients with XLH (a member of the International XLH Alliance), 20 rue Merlin de Thionville, Appt 120, 92150, Suresnes, France.
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Forero-Delgadillo JM, Cleves D, Ochoa V, Londoño-Correa H, Restrepo JM, Nastasi-Catanese JA, Pachajoa H. PHEX Gene Mutation in a Patient with X-Linked Hypophosphatemic Rickets in a Developing Country. Appl Clin Genet 2020; 13:57-62. [PMID: 32104046 PMCID: PMC7025672 DOI: 10.2147/tacg.s232448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/23/2019] [Indexed: 12/03/2022] Open
Abstract
Introduction X-linked hypophosphatemic rickets is part of a larger group of hereditary diseases characterized by renal phosphate loss, which causes growth disorders, rickets, and osteomalacia. These conditions are characterized by disorders in phosphate equilibrium, which is essential for bone formation. Case Report A female patient presented with bone deformities of the inferior extremities, prominent joints, and loss of teeth. She received initial management with oral calcium and orthotics in inferior extremities, with poor clinical outcome. PHEX gene sequencing revealed a pathogenic variant c.1601C>T (p.Pro534Leu). Discussion XLHR is caused by mutations in the PHEX gene; to date, more than 460 mutations have been associated with the disease. Clinically, it is characterized by bowing of the lower extremities, decreased growth, musculoskeletal complaints, dental abscesses, and other clinical signs and symptoms of rickets.
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Affiliation(s)
- Jessica María Forero-Delgadillo
- Pediatric Nephrology Fellow, Universidad Icesi-Fundación Valle de Lili, Cali, Colombia.,Facultad de Ciencias de la Salud, Universidad Icesi, Cali, Colombia
| | - Daniela Cleves
- Facultad de Ciencias de la Salud, Universidad Icesi, Cali, Colombia.,Pediatrics Resident, Universidad Icesi-Fundación Valle de Lili, Cali, Colombia
| | - Vanessa Ochoa
- Pediatric Nephrology Fellow, Universidad Icesi-Fundación Valle de Lili, Cali, Colombia.,Facultad de Ciencias de la Salud, Universidad Icesi, Cali, Colombia
| | | | | | - José Antonio Nastasi-Catanese
- Pediatric Nephrology Department, Fundación Valle del Lili, Cali, Colombia.,Clinical Genetics Department, Fundación Valle del Lili, Cali, Colombia
| | - Harry Pachajoa
- Facultad de Ciencias de la Salud, Universidad Icesi, Cali, Colombia.,Clinical Genetics Department, Fundación Valle del Lili, Cali, Colombia
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Haffner D, Emma F, Eastwood DM, Duplan MB, Bacchetta J, Schnabel D, Wicart P, Bockenhauer D, Santos F, Levtchenko E, Harvengt P, Kirchhoff M, Di Rocco F, Chaussain C, Brandi ML, Savendahl L, Briot K, Kamenicky P, Rejnmark L, Linglart A. Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia. Nat Rev Nephrol 2020; 15:435-455. [PMID: 31068690 PMCID: PMC7136170 DOI: 10.1038/s41581-019-0152-5] [Citation(s) in RCA: 256] [Impact Index Per Article: 64.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care. In this Evidence-Based Guideline on X-linked hypophosphataemia, the authors identify the criteria for diagnosis of this disease, provide guidance for medical and surgical treatment and explain the challenges of follow-up.
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Affiliation(s)
- Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany. .,Center for Congenital Kidney Diseases, Center for Rare Diseases, Hannover Medical School, Hannover, Germany.
| | - Francesco Emma
- Department of Pediatric Subspecialties, Division of Nephrology, Children's Hospital Bambino Gesù - IRCCS, Rome, Italy
| | - Deborah M Eastwood
- Department of Orthopaedics, Great Ormond St Hospital for Children, Orthopaedics, London, UK.,The Catterall Unit Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | - Martin Biosse Duplan
- Dental School, Université Paris Descartes Sorbonne Paris Cité, Montrouge, France.,APHP, Department of Odontology, Bretonneau Hospital, Paris, France.,APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
| | - Justine Bacchetta
- Department of Pediatric Nephrology, Rheumatology and Dermatology, University Children's Hospital, Lyon, France
| | - Dirk Schnabel
- Center for Chronic Sick Children, Pediatric Endocrinology, Charitè, University Medicine, Berlin, Germany
| | - Philippe Wicart
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France.,APHP, Department of Pediatric Orthopedic Surgery, Necker - Enfants Malades University Hospital, Paris, France.,Paris Descartes University, Paris, France
| | - Detlef Bockenhauer
- University College London, Centre for Nephrology and Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Fernando Santos
- Hospital Universitario Central de Asturias (HUCA), University of Oviedo, Oviedo, Spain
| | - Elena Levtchenko
- Department of Pediatric Nephrology and Development and Regeneration, University Hospitals Leuven, University of Leuven, Leuven, Belgium
| | - Pol Harvengt
- RVRH-XLH, French Patient Association for XLH, Suresnes, France
| | - Martha Kirchhoff
- Phosphatdiabetes e.V., German Patient Association for XLH, Lippstadt, Germany
| | - Federico Di Rocco
- Pediatric Neurosurgery, Hôpital Femme Mère Enfant, Centre de Référence Craniosténoses, Université de Lyon, Lyon, France
| | - Catherine Chaussain
- Dental School, Université Paris Descartes Sorbonne Paris Cité, Montrouge, France.,APHP, Department of Odontology, Bretonneau Hospital, Paris, France.,APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
| | - Maria Louisa Brandi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - Lars Savendahl
- Pediatric Endocrinology Unit, Karolinska University Hospital, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - Karine Briot
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France.,Paris Descartes University, Paris, France.,APHP, Department of Rheumatology, Cochin Hospital, Paris, France.,INSERM UMR-1153, Paris, France
| | - Peter Kamenicky
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France.,APHP, Department of Endocrinology and Reproductive Diseases, Bicêtre Paris-Sud Hospital, Paris, France.,INSERM U1185, Bicêtre Paris-Sud, Paris-Sud - Paris Saclay University, Le Kremlin-Bicêtre, France
| | - Lars Rejnmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Agnès Linglart
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France.,INSERM U1185, Bicêtre Paris-Sud, Paris-Sud - Paris Saclay University, Le Kremlin-Bicêtre, France.,APHP, Platform of Expertise of Paris-Sud for Rare Diseases and Filière OSCAR, Bicêtre Paris-Sud Hospital (HUPS), Le Kremlin-Bicêtre, France.,APHP, Endocrinology and Diabetes for Children, Bicêtre Paris-Sud Hospital, Le Kremlin-Bicêtre, France
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Rothenbuhler A, Schnabel D, Högler W, Linglart A. Diagnosis, treatment-monitoring and follow-up of children and adolescents with X-linked hypophosphatemia (XLH). Metabolism 2020; 103S:153892. [PMID: 30928313 DOI: 10.1016/j.metabol.2019.03.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/22/2019] [Accepted: 03/25/2019] [Indexed: 11/19/2022]
Abstract
Early diagnosis, optimal therapeutic management and regular follow up of children with X-linked hypophosphatemia (XLH) determine their long term outcomes and future quality of life. Biochemical screening of potentially affected newborns in familial cases and improving physician's knowledge on clinical signs, symptoms and biochemical characteristics of XLH for de novo cases should lead to earlier diagnosis and treatment initiation. The follow-up of children with XLH includes clinical, biochemical and radiological monitoring of treatment (efficacy and complications) and screening for XLH-related dental, neurosurgical, rheumatological, cardiovascular, renal and ENT complications. In 2018, the European Union approved the use of burosumab, a humanized monoclonal anti-FGF23 antibody, as an alternative therapy to conventional therapy (active vitamin D analogues and phosphate supplements) in growing children with XLH and insufficiently controlled disease. Diagnostic criteria of XLH and the principles of disease management with conventional treatment or with burosumab are reviewed in this paper.
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Affiliation(s)
- Anya Rothenbuhler
- APHP, Endocrinology and Diabetology for Children, Bicêtre Paris Sud Hospital, Le Kremlin-Bicêtre, France; APHP, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, Paris, France; APHP, Platform of Expertise for Rare Disorders Paris-Sud, Bicêtre Paris Sud Hospital, Le Kremlin-Bicêtre, France.
| | - Dirk Schnabel
- Center for Chronic Sick Children, Pediatric Endocrinology, Charité, University Medicine Berlin, Germany
| | - Wolfgang Högler
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Department of Pediatrics and Adolescent Medicine, Johannes Kepler University Linz, Linz, Austria
| | - Agnès Linglart
- APHP, Endocrinology and Diabetology for Children, Bicêtre Paris Sud Hospital, Le Kremlin-Bicêtre, France; APHP, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, Paris, France; APHP, Platform of Expertise for Rare Disorders Paris-Sud, Bicêtre Paris Sud Hospital, Le Kremlin-Bicêtre, France
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Lecoq AL, Brandi ML, Linglart A, Kamenický P. Management of X-linked hypophosphatemia in adults. Metabolism 2020; 103S:154049. [PMID: 31863781 DOI: 10.1016/j.metabol.2019.154049] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/23/2019] [Accepted: 11/25/2019] [Indexed: 11/27/2022]
Abstract
X-linked hypophosphatemia (XLH) is caused by mutations in the PHEX gene which result in Fibroblast Growth Factor-23 (FG-F23) excess and phosphate wasting. Clinically, XLH children present with rickets, bone deformities and short stature. In adulthood, patients may still be symptomatic with bone and joint pain, osteomalacia-related fractures or pseudofractures, precocious osteoarthrosis, enthesopathy, muscle weakness and severe dental anomalies. Besides these musculoskeletal and dental manifestations, adult XLH patients are also prone to secondary and tertiary hyperparathyroidism, cardiovascular and metabolic disorders. Pathophysiology of hyperparathyroidism is only partially understood but FGF23 excess and deficient production of calcitriol likely contributes to its development. Similarly, the pathophysiological mechanisms of potential cardiovascular and metabolic involvements are not clear, but FGF-23 excess may play an essential role. Treatment should be considered in symptomatic patients, patients undergoing orthopedic or dental surgery and women during pregnancy and lactation. Treatment with oral phosphate salts and active vitamin D analogs has incomplete efficacy and potential risks. Burosumab, a recombinant human monoclonal antibody against FGF-23, has proven its efficacy in phase 2 and phase 3 clinical trials in adult patients with XLH, but currently its position as first line or second line treatment differ among the countries.
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Affiliation(s)
- Anne-Lise Lecoq
- AP-HP, Department of Endocrinology and Reproductive Diseases, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France
| | - Maria Luisa Brandi
- Department of Surgery and Translational Medicine, University of Florence, University Hospital of Florence, Florence, Italy
| | - Agnès Linglart
- AP-HP, Endocrinology and Diabetes for Children, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France; Université Paris-Saclay, INSERM, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France
| | - Peter Kamenický
- AP-HP, Department of Endocrinology and Reproductive Diseases, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France; Université Paris-Saclay, INSERM, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France.
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10
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Godfrey EK, Mussa F, Kazahura P, Shoo A, Naburi H, Manji KP. Vitamin D-Resistant Rickets Diagnostics and Treatment Challenges at Muhimbili National Hospital, Tanzania. Case Rep Endocrinol 2020; 2020:1547170. [PMID: 32082647 PMCID: PMC7008276 DOI: 10.1155/2020/1547170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 11/30/2019] [Indexed: 11/17/2022] Open
Abstract
Introduction. Rickets is softening of bones caused by defective mineralization of the cartilage in the epiphyseal growth plate, causing widening of the ends of long bones, growth retardation, and skeletal deformities in children. It can be classified into calciopenic and phosphopenic, each type with various subclasses. Case Presentations. We presented 2 cases, first of a 1 year and 4-month-old male, with a history of recurrent episodes of cough for 8 months and bowing of the legs 6 months prior to admission. Clinical and laboratory investigation was suggestive of vitamin D-dependent rickets, and he started vitamin D treatment with minimal response. The second case is of a 4 years and 7-month-old male who presented with developmental delay, poor weight gain, and recurrent chest infection and worsening of bone pain since 9 months of age. Laboratory investigation was suggestive of phosphopenic rickets, and he was started on treatment at 9 months of age with little improvement and at 4 years, he sustained multiple fractures and succumbed to severe respiratory tract infection and died at 4 years and 7 months of age. CONCLUSION Rickets pose a diagnostic and treatment challenge in resource-limited countries, and clinical judgment and early initiation of treatment are important.
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Affiliation(s)
- Evance K. Godfrey
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
| | - Fatima Mussa
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
| | - Parvina Kazahura
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
| | - Aika Shoo
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
| | - Helga Naburi
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
| | - Karim P. Manji
- Department of Paediatrics and Child Health, Muhimbili University of Health and Allied Sciences (MUHAS), Dar es Salaam, Tanzania
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DeLacey S, Liu Z, Broyles A, El-Azab SA, Guandique CF, James BC, Imel EA. Hyperparathyroidism and parathyroidectomy in X-linked hypophosphatemia patients. Bone 2019; 127:386-392. [PMID: 31276850 PMCID: PMC6836672 DOI: 10.1016/j.bone.2019.06.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 06/18/2019] [Accepted: 06/26/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND X-linked hypophosphatemia (XLH) causes rickets, osteomalacia, skeletal deformities and growth impairment, due to elevated fibroblast growth factor 23 and hypophosphatemia. Conventional therapy requires high doses of phosphate salts combined with active vitamin D analogues. Risks of this regimen include nephrocalcinosis and secondary hyperparathyroidism or progression to tertiary (hypercalcemic) hyperparathyroidism. METHODS The primary goals were to estimate the prevalence of hyperparathyroidism and to characterize parathyroidectomy outcomes regarding hypercalcemia among XLH patients. XLH patients attending our center from 1/2000 to 12/2017 were included in a retrospective chart review. Prevalence of nephrocalcinosis and eGFR < 60 ml/min/1.73m2 was also assessed. RESULTS Of 104 patients with XLH, 84 had concurrent measurements of calcium and PTH (40 adults and 44 children). Of these, 70/84 (83.3%), had secondary or tertiary hyperparathyroidism at any time point. Secondary hyperparathyroidism was persistent in 62.2% of those with data at multiple timepoints. Tertiary hyperparathyroidism had an overall prevalence of 14/84 (16.7%) patients. Parathyroidectomy was performed in 8/84 (9.5%) of the total population. After parathyroidectomy, persistent or recurrent tertiary hyperparathyroidism was detected in 6/8 (75%) patients at a median of 6 years (from 0 to 29 years). One patient had chronic post-surgical hypoparathyroidism and one patient remained normocalcemic 4 years after surgery. Nephrocalcinosis was more prevalent in patients with tertiary hyperparathyroidism than those without (60.0% vs 18.6%). Chronic kidney disease (eGFR < 60 ml/min/1.73m2) was also more prevalent in patients with tertiary hyperparathyroidism than those without (35.7% vs 1.5%). CONCLUSION The majority of patients with XLH develop secondary hyperparathyroidism during treatment with phosphate and active vitamin D. A significant proportion develops tertiary hyperparathyroidism and most have recurrence or persistence of hypercalcemia after surgery.
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Affiliation(s)
- Sean DeLacey
- Indiana University School of Medicine, Department of Medicine, United States of America; Indiana University School of Medicine, Department of Pediatrics, United States of America
| | - Ziyue Liu
- Indiana University School of Public Health, Department of Biostatistics, United States of America
| | - Andrea Broyles
- Regenstrief Institute, Data Core Services, United States of America
| | - Sarah A El-Azab
- Regenstrief Institute, Data Core Services, United States of America
| | | | - Benjamin C James
- Harvard Medical School, Beth Israel Deaconess Medical Center, Department of Surgery, United States of America
| | - Erik A Imel
- Indiana University School of Medicine, Department of Medicine, United States of America; Indiana University School of Medicine, Department of Pediatrics, United States of America.
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12
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Abstract
Fibroblast growth factor 23 (FGF23), one of the endocrine fibroblast growth factors, is a principal regulator in the maintenance of serum phosphorus concentration. Binding to its cofactor αKlotho and a fibroblast growth factor receptor is essential for its activity. Its regulation and interaction with other factors in the bone-parathyroid-kidney axis is complex. FGF23 reduces serum phosphorus concentration through decreased reabsorption of phosphorus in the kidney and by decreasing 1,25 dihydroxyvitamin D (1,25(OH)2D) concentrations. Various FGF23-mediated disorders of renal phosphate wasting share similar clinical and biochemical features. The most common of these is X-linked hypophosphatemia (XLH). Additional disorders of FGF23 excess include autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets, fibrous dysplasia, and tumor-induced osteomalacia. Treatment is challenging, requiring careful monitoring and titration of dosages to optimize effectiveness and to balance side effects. Conventional therapy for XLH and other disorders of FGF23-mediated hypophosphatemia involves multiple daily doses of oral phosphate salts and active vitamin D analogs, such as calcitriol or alfacalcidol. Additional treatments may be used to help address side effects of conventional therapy such as thiazides to address hypercalciuria or nephrocalcinosis, and calcimimetics to manage hyperparathyroidism. The recent development and approval of an anti-FGF23 antibody, burosumab, for use in XLH provides a novel treatment option.
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Affiliation(s)
- Anisha Gohil
- Indiana University School of Medicine, Riley Hospital for Children, Fellow, Endocrinology and Diabetes, 705 Riley Hospital Drive, Room 5960, Indianapolis, IN 46202, USA, E-mail:
| | - Erik A Imel
- Indiana University School of Medicine, Riley Hospital for Children, Associate Professor of Medicine and Pediatrics, 1120 West Michigan Street, CL 459, Indianapolis, IN 46202, USA
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13
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Imel EA, Biggin A, Schindeler A, Munns CF. FGF23, Hypophosphatemia, and Emerging Treatments. JBMR Plus 2019; 3:e10190. [PMID: 31485552 PMCID: PMC6715782 DOI: 10.1002/jbm4.10190] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 02/13/2019] [Accepted: 02/26/2019] [Indexed: 01/03/2023] Open
Abstract
FGF23 is an important hormonal regulator of phosphate homeostasis. Together with its co-receptor Klotho, it modulates phosphate reabsorption and both 1α-hydroxylation and 24-hydroxylation in the renal proximal tubules. The most common FGF23-mediated hypophosphatemia is X-linked hypophosphatemia (XLH), caused by mutations in the PHEX gene. FGF23-mediated forms of hypophosphatemia are characterized by phosphaturia and low or low-normal calcitriol concentrations, and unlike nutritional rickets, these cannot be cured with nutritional vitamin D supplementation. Autosomal dominant and autosomal recessive forms of FGF23-mediated hypophosphatemias show a similar pathophysiology, despite a variety of different underlying genetic causes. An excess of FGF23 activity has also been associated with a number of other conditions causing hypophosphatemia, including tumor-induced osteomalacia, fibrous dysplasia of the bone, and cutaneous skeletal hypophosphatemia syndrome. Historically phosphate supplementation and therapy using analogs of highly active vitamin D (eg, calcitriol, alfacalcidol, paricalcitol, eldecalcitol) have been used to manage conditions involving hypophosphatemia; however, recently a neutralizing antibody for FGF23 (burosumab) has emerged as a promising treatment agent for FGF23-mediated disorders. This review discusses the progression of clinical trials for burosumab for the treatment of XLH and its recent availability for clinical use. Burosumab may have potential for treating other conditions associated with FGF23 overactivity, but these are not yet supported by trial data. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Erik A Imel
- Division of EndocrinologyIndiana University School of Medicine, Indianapolis, INUSA
| | - Andrew Biggin
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Department of EndocrinologyThe Children's Hospital at WestmeadWestmeadAustralia
| | - Aaron Schindeler
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Orthopaedic Research Unit, The Children's Hospital at WestmeadWestmeadAustralia
| | - Craig F Munns
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Department of EndocrinologyThe Children's Hospital at WestmeadWestmeadAustralia
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14
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VanSickle JS, Srivastava T, Alon US. Use of calcimimetics in children with normal kidney function. Pediatr Nephrol 2019; 34:413-422. [PMID: 29552709 DOI: 10.1007/s00467-018-3935-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/22/2018] [Accepted: 02/23/2018] [Indexed: 11/26/2022]
Abstract
The calcium-sensing receptor (CaSR) plays an important role in the homeostasis of serum ionized calcium by regulating parathyroid hormone (PTH) secretion and tubular calcium handling. Calcimimetics, which act by allosteric modulation of the CaSR, mimic hypercalcemia resulting in suppression of PTH release and increase in calciuria. Mostly used in children to treat secondary hyperparathyroidism associated with advanced renal failure, we have shown that calcimimetics can also be successfully used in children with bone and mineral disorders in which elevated PTH plays a detrimental role in skeletal pathophysiology in the face of normal kidney function. The current review briefly discusses the role of the CaSR and calcimimetics in calcium homeostasis, and then addresses the potential applications of calcimimetics in children with normal kidney function with disorders in which suppression of PTH is beneficial.
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Affiliation(s)
- Judith Sebestyen VanSickle
- Bone and Mineral Disorders Clinic, Division of Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, 2401Gillham Road, Kansas City, MO, 64108, USA
| | - Tarak Srivastava
- Bone and Mineral Disorders Clinic, Division of Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, 2401Gillham Road, Kansas City, MO, 64108, USA
- Renal Research Laboratory, Research and Development, Kansas City VA Medical Center, Kansas City, MO, 64128, USA
| | - Uri S Alon
- Bone and Mineral Disorders Clinic, Division of Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, 2401Gillham Road, Kansas City, MO, 64108, USA.
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15
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Abstract
Hypophosphatemic rickets, mostly of the X-linked dominant form caused by pathogenic variants of the PHEX gene, poses therapeutic challenges with consequences for growth and bone development and portends a high risk of fractions and poor bone healing, dental problems and nephrolithiasis/nephrocalcinosis. Conventional treatment consists of PO4 supplements and calcitriol requiring monitoring for treatment-emergent adverse effects. FGF23 measurement, where available, has implications for the differential diagnosis of hypophosphatemia syndromes and, potentially, treatment monitoring. Newer therapeutic modalities include calcium sensing receptor modulation (cinacalcet) and biological molecules targeting FGF23 or its receptors. Their long-term effects must be compared with those of conventional treatments.
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Affiliation(s)
- Martin Bitzan
- Department of Pediatrics, The Montreal Children's Hospital, McGill University Health Centre, 1001 Boulevard Décarie, Room B RC.6164, Montreal, Quebec H4A 3J1, Canada.
| | - Paul R Goodyer
- The Research Institute of the McGill University Health Centre, 1001 Boulevard Décarie, Room EM1.2232, Montreal, Quebec H4A3J1, Canada
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16
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Marcucci G, Masi L, Ferrarì S, Haffner D, Javaid MK, Kamenický P, Reginster JY, Rizzoli R, Brandi ML. Phosphate wasting disorders in adults. Osteoporos Int 2018; 29:2369-2387. [PMID: 30014155 DOI: 10.1007/s00198-018-4618-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/19/2018] [Indexed: 12/14/2022]
Abstract
A cause of hypophosphatemia is phosphate wasting disorders. Knowledge concerning mechanisms involved in phosphate wasting disorders has greatly increased in the last decade by the identification of phosphatonins, among them FGF-23. FGF-23 is a primarily bone derived factor decreasing renal tubular reabsorption of phosphate and the synthesis of calcitriol. Currently, pharmacological treatment of these disorders offers limited efficacy and is potentially associated to gastrointestinal, renal, and parathyroid complications; therefore, efforts have been directed toward newer pharmacological strategies that target the FGF-23 pathway. This review focuses on phosphate metabolism, its main regulators, and phosphate wasting disorders in adults, highlighting the main issues related to diagnosis and current and new potential treatments.
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Affiliation(s)
- G Marcucci
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - L Masi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - S Ferrarì
- Division of Bone Diseases, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - D Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - M K Javaid
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - P Kamenický
- Service d'Endocrinologie et des Maladies de la Reproduction, Centre de référence des Maladies Rares du métabolisme du calcium et du phosphore, Hopital de Bicêtre - AP-HP, 94275, Le Kremlin-Bicêtre, France
| | - J-Y Reginster
- Department of Public Health, Epidemiology and Health Economics, University of Liège, Liège, Belgium
| | - R Rizzoli
- Division of Bone Diseases, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - M L Brandi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
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17
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Imel EA, White KE. Pharmacological management of X-linked hypophosphataemia. Br J Clin Pharmacol 2018; 85:1188-1198. [PMID: 30207609 DOI: 10.1111/bcp.13763] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/05/2018] [Accepted: 09/05/2018] [Indexed: 12/25/2022] Open
Abstract
The most common heritable disorder of renal phosphate wasting, X-linked hypophosphataemia (XLH), was discovered to be caused by inactivating mutations in the phosphate regulating gene with homology to endopeptidases on the X-chromosome (PHEX) gene in 1995. Although the exact molecular mechanisms by which PHEX mutations cause disturbed phosphate handling in XLH remain unknown, focus for novel therapies has more recently been based upon the finding that the bone-produced phosphaturic hormone fibroblast growth factor-23 is elevated in XLH patient plasma. Previous treatment strategies for XLH were based upon phosphate repletion plus active vitamin D analogues, which are difficult to manage, fail to address the primary pathogenesis of the disease, and can have deleterious side effects. A novel therapy for XLH directly targeting fibroblast growth factor-23 via a humanized monoclonal antibody (burosumab-twza/CRYSVITA, henceforth referred to just as burosumab) has emerged as an effective, and recently approved, pharmacological treatment for both children and adults. This review will provide an overview of the clinical manifestations of XLH, the molecular pathophysiology, and summarize its current treatment.
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Affiliation(s)
- Erik A Imel
- Department of Medicine, Division of Endocrinology and Metabolism, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Pediatrics, Section of Endocrinology and Diabetology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, USA
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18
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Auron A, Alon US. Hypercalcemia: a consultant's approach. Pediatr Nephrol 2018; 33:1475-1488. [PMID: 28879535 DOI: 10.1007/s00467-017-3788-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/24/2017] [Accepted: 08/11/2017] [Indexed: 12/11/2022]
Abstract
Due to their daily involvement in mineral metabolism, nephrologists are often asked to consult on children with hypercalcemia. This might become even more pertinent when the hypercalcemia is associated with acute kidney injury and/or hypercalciuria and renal calcifications. The best way to assess the severity of hypercalcemia is by measurement of plasma ionized calcium, and if not available by adjusting serum total calcium to albumin concentration. The differential diagnosis of the possible etiologies of the disturbance in the mineral homeostasis starts with the assessment of serum parathyroid hormone concentration, followed by that of vitamin D metabolites in search of both genetic and acquired etiologies. Several tools are available to acutely treat hypercalcemia with the current main components being fluids, loop diuretics, and antiresorptive agents. This review will address the pathophysiologic mechanisms, clinical manifestations, and treatment modalities involved in hypercalcemia.
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Affiliation(s)
- Ari Auron
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City School of Medicine, 2401 Gillham Road, Kansas City, MO, 64108, USA
| | - Uri S Alon
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City School of Medicine, 2401 Gillham Road, Kansas City, MO, 64108, USA.
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19
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Kinoshita Y, Fukumoto S. X-Linked Hypophosphatemia and FGF23-Related Hypophosphatemic Diseases: Prospect for New Treatment. Endocr Rev 2018; 39:274-291. [PMID: 29381780 DOI: 10.1210/er.2017-00220] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/23/2018] [Indexed: 12/21/2022]
Abstract
Phosphate plays essential roles in many biological processes, and the serum phosphate level is tightly controlled. Chronic hypophosphatemia causes impaired mineralization of the bone matrix and results in rickets and osteomalacia. Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate metabolism. FGF23 excess induces hypophosphatemia via impaired phosphate reabsorption in the renal proximal tubules and decreased phosphate absorption in the intestines. There are several types of genetic and acquired FGF23-related hypophosphatemic diseases. Among these diseases, X-linked hypophosphatemia (XLH), which is caused by inactivating mutations in the phosphate-regulating endopeptidase homolog, X-linked (PHEX) gene, is the most prevalent form of genetic FGF23-related hypophosphatemic rickets. Another clinically relevant form of FGF23-related hypophosphatemic disease is tumor-induced osteomalacia (TIO), a paraneoplastic syndrome associated with FGF23-producing tumors. A combination of active vitamin D and phosphate salts is the current medical therapy used to treat patients with XLH and inoperative TIO. However, this therapy has certain efficacy- and safety-associated limitations. Several measures to inhibit FGF23 activity have been considered as possible new treatments for FGF23-related hypophosphatemic diseases. In particular, a humanized monoclonal antibody for FGF23 (burosumab) is a promising treatment in patients with XLH and TIO. This review will focus on the phosphate metabolism and the pathogenesis and treatment of FGF23-related hypophosphatemic diseases.
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Affiliation(s)
- Yuka Kinoshita
- Division of Nephrology and Endocrinology, Department of Medicine, The University of Tokyo Hospital, Tokyo, Japan
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
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20
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Bacon S, Crowley R. Developments in rare bone diseases and mineral disorders. Ther Adv Chronic Dis 2018; 9:51-60. [PMID: 29344330 PMCID: PMC5761943 DOI: 10.1177/2040622317739538] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 10/04/2017] [Indexed: 12/16/2022] Open
Abstract
In the last decade, there have been a number of significant advances made in the field of rare bone diseases. In this review, we discuss the expansion of the classification system for osteogenesis imperfecta (OI) and the resultant increase in therapeutic options available for management of OI. Bisphosphonates remain the most widely used intervention for OI, although the effect on fracture rate reduction is equivocal. We review the other therapies showing promising results, including denosumab, teriparatide, sclerostin, transforming growth factor β inhibition and gene targeted approaches. X-linked hypophosphataemia (XLH) is the most common heritable form of osteomalacia and rickets caused by a mutation in the phosphate regulating endopeptidase gene resulting in elevated serum fibroblast growth factor 23 (FGF23) and decreased renal phosphate reabsorption. The traditional treatment is phosphate replacement. We discuss the development of a human anti-FGF23 antibody (KRN23) as a promising development in the treatment of XLH. The current management of primary hypoparathyroidism is replacement with calcium and active vitamin D. This can be associated with under or over replacement and its inherent complications. We review the use of recombinant parathyroid hormone (1-84), which can significantly reduce the requirements for calcium and vitamin D resulting in greater safety and quality of life for individuals with hypoparathyroidism. The use of receptor activator of nuclear factor κB ligand infusions in the treatment of a particular form of osteopetrosis and enzyme replacement therapy for hypophosphatasia are also discussed.
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21
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Stokes VJ, Nielsen MF, Hannan FM, Thakker RV. Hypercalcemic Disorders in Children. J Bone Miner Res 2017; 32:2157-2170. [PMID: 28914984 PMCID: PMC5703166 DOI: 10.1002/jbmr.3296] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 09/07/2017] [Accepted: 09/13/2017] [Indexed: 12/20/2022]
Abstract
Hypercalcemia is defined as a serum calcium concentration that is greater than two standard deviations above the normal mean, which in children may vary with age and sex, reflecting changes in the normal physiology at each developmental stage. Hypercalcemic disorders in children may present with hypotonia, poor feeding, vomiting, constipation, abdominal pain, lethargy, polyuria, dehydration, failure to thrive, and seizures. In severe cases renal failure, pancreatitis and reduced consciousness may also occur and older children and adolescents may present with psychiatric symptoms. The causes of hypercalcemia in children can be classified as parathyroid hormone (PTH)-dependent or PTH-independent, and may be congenital or acquired. PTH-independent hypercalcemia, ie, hypercalcemia associated with a suppressed PTH, is commoner in children than PTH-dependent hypercalcemia. Acquired causes of PTH-independent hypercalcemia in children include hypervitaminosis; granulomatous disorders, and endocrinopathies. Congenital syndromes associated with PTH-independent hypercalcemia include idiopathic infantile hypercalcemia (IIH), William's syndrome, and inborn errors of metabolism. PTH-dependent hypercalcemia is usually caused by parathyroid tumors, which may give rise to primary hyperparathyroidism (PHPT) or tertiary hyperparathyroidism, which usually arises in association with chronic renal failure and in the treatment of hypophosphatemic rickets. Acquired causes of PTH-dependent hypercalcemia in neonates include maternal hypocalcemia and extracorporeal membrane oxygenation. PHPT usually occurs as an isolated nonsyndromic and nonhereditary endocrinopathy, but may also occur as a hereditary hypercalcemic disorder such as familial hypocalciuric hypercalcemia, neonatal severe primary hyperparathyroidism, and familial isolated primary hyperparathyroidism, and less commonly, as part of inherited complex syndromic disorders such as multiple endocrine neoplasia (MEN). Advances in identifying the genetic causes have resulted in increased understanding of the underlying biological pathways and improvements in diagnosis. The management of symptomatic hypercalcemia includes interventions such as fluids, antiresorptive medications, and parathyroid surgery. This article presents a clinical, biochemical, and genetic approach to investigating the causes of pediatric hypercalcemia. © 2017 American Society for Bone and Mineral Research.
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Affiliation(s)
- Victoria J Stokes
- Academic Endocrine UnitRadcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Morten F Nielsen
- Academic Endocrine UnitRadcliffe Department of MedicineUniversity of OxfordOxfordUK
- Department of Clinical ResearchFaculty of HealthUniversity of Southern DenmarkOdenseDenmark
| | - Fadil M Hannan
- Academic Endocrine UnitRadcliffe Department of MedicineUniversity of OxfordOxfordUK
- Department of Musculoskeletal BiologyInstitute of Ageing and Chronic DiseaseUniversity of LiverpoolOxfordUK
| | - Rajesh V Thakker
- Academic Endocrine UnitRadcliffe Department of MedicineUniversity of OxfordOxfordUK
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22
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Alon US, Jarka D, Monachino PJ, Sebestyen VanSickle J, Srivastava T. Cinacalcet as an alternative to phosphate therapy in X-linked hypophosphataemic rickets. Clin Endocrinol (Oxf) 2017; 87:114-116. [PMID: 28382624 DOI: 10.1111/cen.13346] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Uri S Alon
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, Kansas City, MO, USA
| | - Dale Jarka
- Department of Pediatric Orthopedics, Children's Mercy Hospital, University of Missouri at Kansas City, Kansas City, MO, USA
| | - Penny J Monachino
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, Kansas City, MO, USA
| | - Judith Sebestyen VanSickle
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, Kansas City, MO, USA
| | - Tarak Srivastava
- Bone and Mineral Disorders Clinic, Division of Pediatric Nephrology, Children's Mercy Hospital, University of Missouri at Kansas City, Kansas City, MO, USA
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23
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Abstract
Fibroblast growth factor 23 (FGF23) is an important regulator of phosphate and vitamin D metabolism and its excessive or insufficient production leads to a wide variety of skeletal disorders. This article reviews the FGF23-α-Klotho signaling pathway, highlighting the latest developments in FGF23 regulation and action, and describes the disorders associated with FGF23 excess or deficiency.
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Affiliation(s)
- Anda R Gonciulea
- Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Suzanne M Jan De Beur
- Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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24
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Rafaelsen S, Johansson S, Ræder H, Bjerknes R. Hereditary hypophosphatemia in Norway: a retrospective population-based study of genotypes, phenotypes, and treatment complications. Eur J Endocrinol 2016; 174:125-36. [PMID: 26543054 PMCID: PMC4674593 DOI: 10.1530/eje-15-0515] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 11/04/2015] [Indexed: 01/14/2023]
Abstract
OBJECTIVE Hereditary hypophosphatemias (HH) are rare monogenic conditions characterized by decreased renal tubular phosphate reabsorption. The aim of this study was to explore the prevalence, genotypes, phenotypic spectrum, treatment response, and complications of treatment in the Norwegian population of children with HH. DESIGN Retrospective national cohort study. METHODS Sanger sequencing and multiplex ligand-dependent probe amplification analysis of PHEX and Sanger sequencing of FGF23, DMP1, ENPP1KL, and FAM20C were performed to assess genotype in patients with HH with or without rickets in all pediatric hospital departments across Norway. Patients with hypercalcuria were screened for SLC34A3 mutations. In one family, exome sequencing was performed. Information from the patients' medical records was collected for the evaluation of phenotype. RESULTS Twety-eight patients with HH (18 females and ten males) from 19 different families were identified. X-linked dominant hypophosphatemic rickets (XLHR) was confirmed in 21 children from 13 families. The total number of inhabitants in Norway aged 18 or below by 1st January 2010 was 1,109,156, giving an XLHR prevalence of ∼1 in 60,000 Norwegian children. FAM20C mutations were found in two brothers and SLC34A3 mutations in one patient. In XLHR, growth was compromised in spite of treatment with oral phosphate and active vitamin D compounds, with males tending to be more affected than females. Nephrocalcinosis tended to be slightly more common in patients starting treatment before 1 year of age, and was associated with higher average treatment doses of phosphate. However, none of these differences reached statistical significance. CONCLUSIONS We present the first national cohort of HH in children. The prevalence of XLHR seems to be lower in Norwegian children than reported earlier.
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Affiliation(s)
- Silje Rafaelsen
- Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway
| | - Stefan Johansson
- Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway
| | - Helge Ræder
- Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway
| | - Robert Bjerknes
- Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway Section for PediatricsDepartment of Clinical Science, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayCenter for Medical Genetics and Molecular MedicineDepartment of PediatricsHaukeland University Hospital, Bergen, Norway
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Carpenter TO, Olear EA, Zhang JH, Ellis BK, Simpson CA, Cheng D, Gundberg CM, Insogna KL. Effect of paricalcitol on circulating parathyroid hormone in X-linked hypophosphatemia: a randomized, double-blind, placebo-controlled study. J Clin Endocrinol Metab 2014; 99:3103-11. [PMID: 25029424 PMCID: PMC4154090 DOI: 10.1210/jc.2014-2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
CONTEXT Hyperparathyroidism occurs frequently in X-linked hypophosphatemia (XLH) and may exacerbate phosphaturia, potentially affecting skeletal abnormalities. OBJECTIVE The objective of the study was to suppress elevated PTH levels in XLH patients. DESIGN This was a prospective, randomized, placebo-controlled, double-blind, 1-year trial of paricalcitol, with outcomes measured at entry and 1 year later. SETTING PATIENTS were recruited from the investigators' clinics or referred from throughout the United States. Data were collected in an in-patient hospital research unit. PATIENTS Subjects with a clinical diagnosis of XLH and hyperparathyroidism were offered participation and were eligible if they were 9 years old or older and not pregnant, and their serum calcium level was less than 10.7 mg/dL, their 25-hydroxyvitamin D level was 20 ng/mL or greater, and their creatinine level was 1.5 mg/dL or less. INTERVENTION The intervention for this study was the use of paricalcitol or placebo for 1 year. MAIN OUTCOME MEASURES Determined prior to trial onset was the change in PTH area under the curve. Secondary outcomes included renal phosphate threshold per glomerular filtration rate, serum phosphorus, serum alkaline phosphatase activity, and (99m)Tc-methylenediphosphonate bone scans. RESULTS PTH area under the curve decreased 17% with paricalcitol, differing (P = .007) from the 20% increase with placebo. The renal phosphate threshold per glomerular filtration rate increased 17% with paricalcitol and decreased 21% with placebo (P = .05). Serum phosphorus increased 12% with paricalcitol but did not differ from placebo. Paricalcitol decreased alkaline phosphatase activity in adults by 21% (no change with placebo, P = .04). Bone scans improved in 6 of 17 paricalcitol subjects, whereas no placebo-treated subject improved. Hypercalciuria developed in six paricalcitol subjects and persisted from baseline in one placebo subject. CONCLUSIONS Suppression of PTH may be a useful strategy for skeletal improvement in XLH patients with hyperparathyroidism, and paricalcitol appears to be an effective adjunct to standard therapy in this setting. Although paricalcitol was well tolerated, urinary calcium and serum calcium and creatinine should be monitored closely with its use.
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Affiliation(s)
- Thomas O Carpenter
- Departments of Pediatrics (Endocrinology) (T.O.C., E.A.O., B.K.E.), Internal Medicine (Endocrinology) (C.A.S., K.L.I.), Orthopaedics and Rehabilitation (T.O.C., C.M.G.), and Diagnostic Radiology (Nuclear Medicine) (D.C.), Yale University School of Medicine, New Haven, Connecticut 06520; and the Veterans Administration Cooperative Studies Program Coordinating Center (JHZ), Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut 06516
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26
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Crowley RK, Kilbane M, King TFJ, Morrin M, O’Keane M, McKenna MJ. Hungry bone syndrome and normalisation of renal phosphorus threshold after total parathyroidectomy for tertiary hyperparathyroidism in X-linked hypophosphataemia: a case report. J Med Case Rep 2014; 8:84. [PMID: 24594262 PMCID: PMC3946034 DOI: 10.1186/1752-1947-8-84] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 12/20/2013] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION This is the first report of which the authors are aware to describe this c.2166delinsGG mutation in X-linked hypophosphataemia and to describe normalisation of renal threshold for phosphate excretion after parathyroidectomy for tertiary hyperparathyroidism in X-linked hypophosphataemia. CASE PRESENTATION We present the case of a 34-year-old Caucasian woman with X-linked hypophosphataemia. She developed tertiary hyperparathyroidism with markedly high bone turnover requiring total parathyroidectomy and had prolonged requirement for intravenous calcium infusion after surgery. She had a novel mutation in her phosphate-regulating gene with homologies to endopeptidases on the X-chromosome and had an unusual degree of dependence on phosphate supplementation. Prior to operative intervention she had a trial of cinacalcet that improved bone turnover markers when used in isolation but which led to a paradoxical rise in parathyroid hormone levels when given with phosphate supplementation. After correction of hungry bone syndrome, the renal phosphorus threshold normalised as a manifestation of hypoparathyroid state despite marked elevation in level of fibroblast growth factor 23. CONCLUSIONS This case illustrates the risk of tertiary hyperparathyroidism as a complication of treatment for hypophosphataemia; it highlights the morbidity associated with hungry bone syndrome and provides novel insight into renal handling of phosphorus.
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Affiliation(s)
- Rachel K Crowley
- Department of Endocrinology, St. Vincent’s University Hospital, Dublin, Ireland
| | - Mark Kilbane
- Metabolism Laboratory, St. Vincent’s University Hospital, Dublin, Ireland
| | - Thomas FJ King
- Department of Endocrinology, St. Vincent’s University Hospital, Dublin, Ireland
| | - Michelle Morrin
- Metabolism Laboratory, St. Vincent’s University Hospital, Dublin, Ireland
| | - Myra O’Keane
- Metabolism Laboratory, St. Vincent’s University Hospital, Dublin, Ireland
| | - Malachi J McKenna
- Department of Endocrinology, St. Vincent’s University Hospital, Dublin, Ireland
- Metabolism Laboratory, St. Vincent’s University Hospital, Dublin, Ireland
- DXA Unit, St. Vincent’s University Hospital, Dublin, Ireland
- School of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland
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Three-year successful cinacalcet treatment of secondary hyperparathyroidism in a patient with x-linked dominant hypophosphatemic rickets: a case report. Case Rep Endocrinol 2014; 2014:479641. [PMID: 24660072 PMCID: PMC3934321 DOI: 10.1155/2014/479641] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/03/2014] [Indexed: 11/18/2022] Open
Abstract
Hypophosphatemic rickets (HR) is a rare inherited disorder characterized by a classic rickets phenotype with low plasma phosphate levels and resistance to treatment with vitamin D. Development of secondary hyperparathyroidism (SHPT) as a direct consequence of treatment is a frequent complication and a major clinical challenge, as this may increase risk of further comorbidity. Cinacalcet, a calcimimetic agent that reduces the secretion of PTH from the parathyroid glands, has been suggested as adjuvant treatment to SHPT in patients with HR. However, only two papers have previously been published and no data are available on effects of treatment for more than six months. We now report a case of 3-year treatment with cinacalcet in a patient with HR complicated by SHPT. A 53-year-old woman with genetically confirmed X-linked dominant hypophosphatemic rickets developed SHPT after 25 years of conventional treatment with alfacalcidol and phosphate supplements. Cinacalcet was added to her treatment, causing a sustained normalization of PTH. Ionized calcium decreased, requiring reduction of cinacalcet, though asymptomatical. Level of phosphate was unchanged, but alkaline phosphatase increased in response to treatment. Cinacalcet appeared to be efficient, safe, and well tolerated. We recommend close control of plasma calcium to avoid hypocalcemia.
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Freudlsperger C, Hoffmann J, Castrillon-Oberndorfer G, Engel M. Bilateral coronal and sagittal synostosis in X-linked hypophosphatemic rickets: a case report. J Craniomaxillofac Surg 2013; 41:842-4. [PMID: 23466123 DOI: 10.1016/j.jcms.2013.01.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 01/07/2013] [Accepted: 01/07/2013] [Indexed: 11/25/2022] Open
Abstract
Craniosynostosis can be gene-linked, or caused by metabolic diseases, such as rickets, which results from a deficiency or impaired metabolism of vitamin D, magnesium, phosphorus or calcium leading to hypomineralization of the bone. X-linked dominant hypophosphatemic rickets (XLHR) is the most prevalent genetic type of hypophosphatemic rickets and is caused by germ line mutations in the PHEX-gene. In XLHR, only few case reports of craniosynostosis were described. Here, we present a clinical report of an 18 months old child with XLHR and bilateral coronal and sagittal synostosis who was treated by subtotal cranial vault remodelling with fronto-orbital advancement and right-angled Z-osteotomies. As a consequence of the child's diminished bone regeneration capacity, surgery that is performed after the age of 1 year requires more extensive craniectomy, multiple osteotomies and rigid fixation for calvarial vault remodelling to prevent extensive bone defects.
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Paravertebral ligament ossification in vitamin D-resistant rickets: incidence, clinical significance, and genetic evaluation. Spine (Phila Pa 1976) 2012; 37:E792-6. [PMID: 22261628 DOI: 10.1097/brs.0b013e31824a3dc8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN A retrospective observational study. OBJECTIVE The objective of this study was to analyze the cases of paravertebral ossification in vitamin D-resistant rickets (VDRR) and elucidate its incidence and clinical significance, and report specific genetic mutations uniquely associated with this phenomenon. SUMMARY OF BACKGROUND DATA Paravertebral ligament ossification has been described in VDRR in a few cases previously. However, supraspinous and interspinous ligament ossification has so far not been described to occur in association with VDRR. We reviewed 6 cases of paravertebral ligament ossification with the added feature of supraspinous and interspinous ligament calcification. METHODS Forty-four patients with clinical, radiological, and biochemical diagnoses of VDRR, who were positive for mutations in the PHEX gene, were screened for the presence of paravertebral ossification with plain radiographs and computed tomography/magnetic resonance imaging if necessary. This was correlated with the severity of disease, and we looked for specific genetic mutations. RESULTS Six patients had paravertebral ligament ossification, which included supraspinous and interspinous ligament ossification. These patients had a more severe systemic disease, with all patients requiring at least 1 surgery for deformity correction of the limbs, with a total of 10 surgical procedures performed in these 6 patients. c.1601C>T, c.1699C>T, c.1363G>T, and c.466_467insAC were the genetic mutations associated with these cases. CONCLUSION The spinal changes with paravertebral ligament ossification in VDRR were described in this study. Four different gene mutations related to the PHEX gene were detected in them. The presence of these changes was suggestive of a more severe systemic disease.
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Abstract
Rickets is disorder of a growing child arising from disorders that result in impaired apoptosis of hypertrophic cells and mineralization of the growth plate. Rickets due to nutritional causes remains an important global problem. The factors responsible for resurgence of rickets among dark-skinned infants living in developed countries include the following: residence in northern or southern latitudes, voluntary avoidance of exposure to solar ultraviolet B radiation, maternal vitamin D deficiency during pregnancy, and prolonged breastfeeding without provision of vitamin D supplements. Fibroblast growth factor 23 (FGF23), secreted by osteocytes, is an important regulator of serum phosphate and 1,25(OH)(2)D(3) levels. Hypophosphatemic rickets resulting from increased synthesis or under-catabolism of FGF23 is reviewed.
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Affiliation(s)
- M Zulf Mughal
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Oxford Road, Manchester, M13 9WL, UK.
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Rajah J, Thandrayen K, Pettifor JM. Clinical practice: diagnostic approach to the rachitic child. Eur J Pediatr 2011; 170:1089-96. [PMID: 21833499 DOI: 10.1007/s00431-011-1529-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 06/28/2011] [Indexed: 11/30/2022]
Abstract
Rickets remains a common problem among infants and children in many countries worldwide. Although the classical presentation associated with bone abnormalities is well known, paediatricians need to be aware of atypical presentations, especially in the first 6 months of life. Furthermore, although vitamin D deficiency rickets remains the commonest form of rickets in most countries, health care providers need to be aware of other possible causes and their typical clinical and biochemical presentations. This article discusses these and highlights the characteristic features of various forms of rickets and possible pitfalls clinicians should be aware of when confronted with a patient with suspected rickets. In conclusion, the recent advances made in understanding the underlying pathogeneses of the various forms of rickets has helped to delineate the diagnostic tests that assist in the diagnosis and management of the disease in children.
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Affiliation(s)
- Jaishen Rajah
- Department of Pediatrics, Sheikh Khalifa Medical City, Abu Dhabi, United Arab Emirates
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Abstract
Tumor-induced osteomalacia (TIO) is a rare and fascinating paraneoplastic syndrome in which patients present with bone pain, fractures, and muscle weakness. The cause is high blood levels of the recently identified phosphate and vitamin D-regulating hormone, fibroblast growth factor 23 (FGF23). In TIO, FGF23 is secreted by mesenchymal tumors that are usually benign, but are typically very small and difficult to locate. FGF23 acts primarily at the renal tubule and impairs phosphate reabsorption and 1α-hydroxylation of 25-hydroxyvitamin D, leading to hypophosphatemia and low levels of 1,25-dihydroxy vitamin D. A step-wise approach utilizing functional imaging (F-18 fluorodeoxyglucose positron emission tomography and octreotide scintigraphy) followed by anatomical imaging (computed tomography and/or magnetic resonance imaging), and, if needed, selective venous sampling with measurement of FGF23 is usually successful in locating the tumors. For tumors that cannot be located, medical treatment with phosphate supplements and active vitamin D (calcitriol or alphacalcidiol) is usually successful; however, the medical regimen can be cumbersome and associated with complications. This review summarizes the current understanding of the pathophysiology of the disease and provides guidance in evaluating and treating these patients. Novel imaging modalities and medical treatments, which hold promise for the future, are also reviewed.
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Affiliation(s)
- William H Chong
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, Hatfield Clinical Research Center, National Institutes of Health, Bethesda, Maryland 20892, USA
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