Explore the vast range of titles available.

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.

The authors describe a germ-line mutation in the gene for PRKAR1A in three unrelated patients with acrodysostosis and resistance to multiple hormones. The mutated protein subunit impairs the response of protein kinase A to cyclic-AMP stimulation. Numerous hormones activate heterotrimeric G-protein–coupled receptors, which then activate G protein and adenylyl cyclase, generating intracellular cAMP. 1 In turn, cAMP activates protein kinase A, resulting in the phosphorylation of specific proteins that mediate the physiological effects of these hormones. 2 – 4 Loss-of-function mutations in the gene encoding GNAS cause pseudohypoparathyroidism type 1a, a disease with characteristic developmental and skeletal abnormalities (collectively called Albright's hereditary osteodystrophy, i.e., short stature, brachydactyly most frequently affecting the fourth and fifth metacarpals, rounded facies, obesity, and heterotopic subcutaneous ossification) that are associated with hormone resistance. 1 , 5 Acrodysostosis (Online Mendelian Inheritance in Man number 101800) is a . . .

Hypophosphatasia is a rare genetic disorder of calcium and phosphate metabolism due to ALPL gene mutations, which leads to abnormal mineralization of the bones and teeth. Hypophosphatasia is characterized by low serum alkaline phosphatase activity and a number of clinical signs, including failure to thrive, bone pain and dental issues. The diagnosis is suspected based on clinical, laboratory and imaging findings and confirmed by genetic testing. Diagnosis in children is often delayed due to a lack of disease awareness, despite specific imaging findings that are a cornerstone of the diagnosis. The recent approval of enzyme replacement therapy (bone-targeted recombinant tissue nonspecific alkaline phosphatase) has given imaging an important role in monitoring treatment efficacy. The aim of this pictorial essay is to review the imaging features of hypophosphatasia at diagnosis and during follow-up, including whole-body magnetic resonance imaging patterns.

Silver-Russell syndrome (SRS) (mainly secondary to 11p15 molecular disruption) and Temple syndrome (TS) (secondary to 14q32.2 molecular disruption) are imprinting disorders with phenotypic (prenatal and postnatal growth retardation, early feeding difficulties) and molecular overlap. To describe the clinical overlap between SRS and TS and extensively study the molecular aspects of TS. We retrospectively collected data on 28 patients with disruption of the 14q32.2 imprinted region, identified in our center, and performed extensive molecular analysis. Seventeen (60.7%) patients showed loss of methylation of the MEG3/DLK1 intergenic differentially methylated region by epimutation. Eight (28.6%) patients had maternal uniparental disomy of chromosome 14 and three (10.7%) had a paternal deletion in 14q32.2. Most patients (72.7%) had a Netchine-Harbison SRS clinical scoring system ≥4/6, and consistent with a clinical diagnosis of SRS. The mean age at puberty onset was 7.2 years in girls and 9.6 years in boys; 37.5% had premature pubarche. The body mass index of all patients increased before pubarche and/or the onset of puberty. Multilocus analysis identified multiple methylation defects in 58.8% of patients. We identified four potentially damaging genetic variants in genes encoding proteins involved in the establishment or maintenance of DNA methylation. Most patients with 14q32.2 disruption fulfill the criteria for a clinical diagnosis of SRS. These clinical data suggest similar management of patients with TS and SRS, with special attention to their young age at the onset of puberty and early increase of body mass index.

The bioactive vitamin D 3 , 1α,25(OH) 2 D 3 , plays a central role in calcium homeostasis by controlling the activity of the vitamin D receptor (VDR) in various tissues. Hypercalcemia secondary to high circulating levels of vitamin D 3 leads to hypercalciuria, nephrocalcinosis and renal dysfunctions. Current therapeutic strategies aim at limiting calcium intake, absorption and resorption, or 1α,25(OH) 2 D 3 synthesis, but are poorly efficient. In this study, we identify WBP4 as a new VDR interactant, and demonstrate that it controls VDR subcellular localization. Moreover, we show that the vitamin D analogue ZK168281 enhances the interaction between VDR and WBP4 in the cytosol, and normalizes the expression of VDR target genes and serum calcium levels in 1α,25(OH) 2 D 3 -intoxicated mice. As ZK168281 also blunts 1α,25(OH) 2 D 3 -induced VDR signaling in fibroblasts of a patient with impaired vitamin D degradation, this VDR antagonist represents a promising therapeutic option for 1α,25(OH) 2 D 3 -induced hypercalcemia. Current therapeutic strategies for vitamin D-induced hypercalcemia are poorly efficient. Here the authors identify a new interaction between the vitamin D receptor (VDR) and WBP4 controlling the subcellular localization of VDR and show that ZK168281, a VDR antagonist, enhances the interaction between VDR and WBP4 blunting VDR signalling and normalizing calcium levels in vitamin D-intoxicated mice.

In patients with X-linked hypophosphatemia, which is caused by PHEX mutations and is characterized by high FGF-23 and rickets, burosumab, an FGF-23 monoclonal antibody, improved renal phosphate reabsorption, serum phosphorus levels, and linear growth and reduced rickets severity.

X-linked hypophosphataemia is a genetic disease caused by defects in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene and is characterised by X-linked dominant inheritance. The main consequence of PHEX deficiency is increased production of the phosphaturic hormone fibroblast growth factor 23 (FGF23) in osteoblasts and osteocytes. Chronic exposure to circulating FGF23 is responsible for renal phosphate wasting and decreased synthesis of calcitriol, which decreases intestinal phosphate absorption. These mechanisms result in lifelong hypophosphataemia, impaired growth plate and bone matrix mineralisation, and diverse manifestations in affected children and adults, including some debilitating morbidities and possibly increased mortality. Important progress has been made in disease knowledge and management over the past decade; in particular, targeting FGF23 is a therapeutic approach that has substantially improved outcomes. However, patients affected by this complex disease need lifelong care and innovative treatment strategies, such as gene repair of PHEX, are necessary to further limit the disease burden.

Background Hypophosphatasia (HPP) is a rare, systemic disease caused by mutation(s) within the ALPL gene encoding tissue-nonspecific alkaline phosphatase (ALP). HPP has a heterogeneous presentation, which coupled with its rarity, often leads to missed/delayed diagnosis and an incomplete understanding of its natural history. To better understand the epidemiology and clinical course of HPP, including timing of diagnosis after first reported manifestation, we present baseline data for patients enrolled in the Global HPP Registry. Methods Data were analyzed from patients with an HPP diagnosis confirmed by low serum ALP activity and/or an ALPL pathogenic variant, regardless of prior or current treatment, according to age at enrollment (children: < 18 y; adult: ≥18 y). All analyses were descriptive. Results Of 269 patients from 11 countries enrolled January 2015–September 2017, 121 (45.0%) were children and 148 (55.0%) were adults. The majority of children and adults were female (61.2 and 73.0%, respectively) and white (57.7 and 90.0%, respectively). Children had a median (min, max) age at earliest reported HPP manifestation of 7.2 months (− 2.3 mo, 16.0 y), which was > 12 months before diagnosis at age 20.4 months (− 0.2 mo, 16.0 y). In adults, the earliest reported manifestation occurred at a median (min, max) age of 37.6 years (0.2 y, 75.2 y), which preceded age at diagnosis (47.5 years [0.2 y, 75.2 y]) by ~ 10 years. Premature loss of deciduous teeth (48.2%, age ≥ 6 mo), bone deformity (32.5%), and failure to thrive (26.7%) were most commonly reported in the HPP-related disease history of children. Pain (74.5%), orthopedic procedures and therapies (44.6%), and recurrent and poorly healing fractures (36.5%) were most commonly reported in the HPP-related disease history of adults. Conclusions The Global HPP Registry represents the largest observational study of patients with HPP, capturing real world data. This analysis shows that diagnostic delay is common, reflecting limited awareness of HPP, and that HPP is associated with systemic manifestations across all ages. Many patients diagnosed in adulthood had HPP manifestations in childhood, highlighting the importance of taking thorough medical histories to ensure timely diagnosis. Trial registration Clinicaltrials.gov : NCT02306720 , December 2014; ENCePP.eu: EUPAS13526 , May 2016 (retrospectively registered).

Abstract Context Serum calcium is frequently measured during the neonatal period, and it is known to be influenced by the vitamin D status. Objective We hypothesized that the 25-hydroxyvitamin D (25OHD) concentration may influence the lower limit of the serum calcium normal range in neonates. Methods We included in our prospective cohort study 1002 mother-newborn pair recruited from April 2012 to July 2014, in 2 centers located in the neighborhoods of Paris, France, whose serum calcium was measured at 3 days of life. We established, after exclusion of outliers, a 95% CI for serum calcium (i) in our whole population of 1002 neonates; (ii) in neonates with a cord blood 25OHD concentration ≥ 30 nmol/L; and (iii) in those with a 25OHD ≥ 50 nmol/L. Results The mean serum total calcium was 2.46 ± 0.13 nmol/L (95% CI: 2.19-2.72 mmol/L), 2.47 ± 0.25 mmol/L (95% CI: 2.22-2.72 mmol/L), and 2.50 ± 0.25 mmol/L (95% CI: 2.25-2.75 mmol/L) in the whole group, in the 514 neonates with 25OHD ≥ 30 nmol/L, and in the 202 neonates with 25OHD ≥ 50 nmol/L respectively. The lower limit of the 95% range was significantly higher in neonates with 25 OHD ≥ 30 nmol/L (P < 0.05) and ≥ 50 nmol/L (P < .001) than in the entire cohort. Conclusion We show that the lower limit of the normal serum calcium range is higher in groups with a higher 25OHD than in unselected subjects. We propose that the reference range for serum calcium in neonates is 2.25 to 2.75 mmol/L.