Prevalence of hearing loss in pseudohypoparathyroidism.

BACKGROUND: The main clinical features of pseudohypoparathyroidism (PHP)/inactivating parathyroid hormone/parathyroid hormone-related protein signaling disorders (iPPSD), including parathyroid hormone (PTH) resistance, brachydactyly and short stature, develop during middle and late childhood. Very few studies have addressed hearing loss in PHP/iPPSD patients, and these studies have yielded widely divergent conclusions. The aim of our study was to assess hearing and determine the predictive factors of hearing loss in patients with PHP/iPPSD. METHODS: Our retrospective cohort study was conducted between March 2019 and May 2020 in the Otolaryngology Department and the calcium phosphate reference center for rare diseases in Bicêtre Paris-Saclay Hospital, France. We retrospectively collected data from patients with PHP/iPPSDs (age, sex, genetic mutations, height, body mass index (BMI), PTH resistance, presence or absence of ectopic ossifications and brachydactyly). All patients underwent auditory investigations, including tonal and vocal audiometry. The primary outcome was the pure tone average (PTA). The PTA was compared with the norm according to the International Organization for Standardization. Hearing loss was defined as a PTA ≥ 20 db. RESULTS: The median age of the patients was 15.6 years [9.5, 28.5]. Thirty-six patients were diagnosed with iPPSD2, and eight were diagnosed with iPPSD3. Twenty-six of them (59%) were female. Hearing impairment was confirmed in 17 patients (39%). The mean PTA and the mean SRT of the deaf ears were 40 ± 26 db and 31 ± 14 db. The mean difference in the PTA between the patients and the normal controls was 11.4 db (p = 0.00002). Short stature and the presence of ectopic ossifications were two significant predictive factors of hearing loss (p = 0.009 and p = 0.03, respectively). Sex, BMI, PTH resistance, mutation category and brachydactyly were not associated with an increased risk of hearing loss (p = 0.19, p = 0.41, p = 0.13, p = 0.50, p = 0.19, respectively). CONCLUSION: Our study confirmed the frequency of hearing loss in patients with PHP/iPPSD disease (prevalence = 39%). A diagnosis of PHP/iPPSD should trigger auditory investigations and follow-up, especially when short stature and/or ectopic ossifications are present.

Somapacitan in Children Born SGA: 52-week Efficacy, Safety, and IGF-I Response Results from the Phase 2 REAL5 Study.

CONTEXT: Somapacitan, a once-weekly reversible albumin-binding GH derivative, is evaluated in short children born small for gestational age (SGA). OBJECTIVE: Evaluate efficacy, safety, tolerability as well as total and bioactive insulin-like growth factor-I (IGF-I) response of once-weekly somapacitan compared to daily GH in children born SGA. METHODS: REAL5 is a randomized, multi-center, open-label, controlled phase 2 study comprising a 26-week main phase, 26-week extension, and an ongoing 4-year safety extension (NCT03878446). SETTING: Thirty-eight sites across 12 countries. PATIENTS: Sixty-two GH-treatment-naïve, prepubertal short children born SGA were randomized; 61 completed 52-weeks of treatment. INTERVENTIONS: Patients randomized (1:1:1:1:1) to somapacitan (0.16, 0.20 or 0.24 mg/kg/week) or daily GH (0.035 or 0.067 mg/kg/day), all administered subcutaneously. RESULTS: Estimated mean height velocity (HV; cm/year) at week 52 was 8.5, 10.4 and 10.7 cm/year for somapacitan 0.16, 0.20 and 0.24 mg/kg/week, respectively, and 9.3 and 11.2 cm/year for daily GH 0.035 and 0.067 mg/kg/day, respectively. Dose-dependent increases in total IGF-I as well as peak IGF-I bioactivity were observed for both treatments and were similar between comparator groups. For somapacitan, exposure-response modelling indicated highest efficacy with 0.24 mg/kg/week after 52 weeks of treatment. Similar safety and tolerability were demonstrated across all groups. CONCLUSIONS: A sustained dose-dependent growth response was demonstrated for somapacitan after 52 weeks of treatment. Overall, somapacitan 0.24 mg/kg/week provides similar efficacy, safety, and tolerability, as well as comparable bioactive and total IGF-I response, as daily GH (0.067 mg/kg/day) in children born SGA.

Metabolically healthy obesity in adults with X-linked hypophosphatemia.

OBJECTIVES: X-linked hypophosphatemia (XLH) is characterized by increased concentrations of circulating fibroblast growth factor 23 (FGF-23) resulting in phosphate wasting, hypophosphatemia, atypical growth plate and bone matrix mineralization. Epidemiologic studies suggest a relationship between FGF-23, obesity, and metabolic dysfunction. The prevalence of overweight and obesity is high in children with XLH. We aimed to evaluate the prevalence of obesity and metabolic complications in adults with XLH. METHODS: We conducted a prospective cohort study in adult XLH patients from a single tertiary referral center. The proportion of patients with a BMI >25 kg/m2 was the main outcome measure. Body fat mass percentage (FM%) and adipose tissue surfaces were secondary outcome measures. Glucose homeostasis (plasma glucose and insulin concentrations after fasting and 2 hours after an oral glucose tolerance test) was explored in a subgroup of patients and compared with age-, sex-, and BMI-matched healthy controls. RESULTS: Among 113 evaluated patients, 85 (75%) were female and 110 (97%) carried a PHEX mutation. Sixty-three (56%) patients were overweight or obese, with a median BMI of 25.3 [IQR, 22.7; 29.2] kg/m2. BMI was correlated with FM%, abdominal and thigh subcutaneous and intra-abdominal adipose tissue surfaces. The prevalence of impaired fasting glucose, impaired glucose tolerance, and diabetes was not different between XLH patients and matched controls. CONCLUSION: The prevalence of overweight and obesity is high among XLH patients and is associated with excess fat mass. However, the prevalence of glucose homeostasis abnormalities is not increased in patients compared to healthy controls, suggesting that metabolically healthy overweight or obesity predominates.

Characterization of Digestive Manifestations in Patients with Impaired PTH/PTHrP Signaling Disorder/Pseudohypoparathyroidism.

INTRODUCTION: Pseudohypoparathyroidism, newly classified as inactivating PTH/PTHrP signaling disorder (iPPSD) type 2 or type 3, is a rare disease caused by defects in the GNAS imprinted gene that encodes Gsα. The most common phenotype comprises resistance to hormones binding to G protein-coupled receptors such as PTH, PTHrP, or TSH, subcutaneous ossifications, short stature, brachydactyly, and early onset obesity. Uncommon features have been described including sleep apnea, asthma, and resistance to calcitonin. At the national French reference center for rare calcium and phosphate metabolism diseases, a large cohort of patients with iPPSD type 2 and type 3 is followed. Interestingly, digestive manifestations and in particular intractable constipation were regularly reported by families of children with iPPSD type 2 or type 3. OBJECTIVE: The aim of our study was therefore to specify the frequency and characteristics of digestive manifestations in children followed up for iPPSD2 or iPPSD3 in our reference center. MATERIAL AND METHODS: Thirty-six patients aged between 2 and 18 years (32 followed up for iPPSD2 and 4 for iPPSD3) were included. Parents completed a specific questionnaire to assess any digestive disorders in their child. The diagnosis of constipation was established using the Bristol visual scale in the event of a score of less than 2 according to stool appearance. RESULTS: Parents reported constipation through the questionnaires in 22/36 (over 60%) of the children. It was the most frequently reported digestive disorder. Among these 22 children, 19 (87%) had a Bristol score for stool shape and texture between 1 and 2 on a scale of 7, confirming constipation. Dedicated treatment had been initiated for 10 (55%) of them, yet only 3 families (16%) considered this treatment effective. Neonatal vomiting and eating disorders, such as lack of satiety or food selectivity, were also noted in 18 (50%) of patients, as was gastroesophageal reflux present in the neonatal period in 14 (40%) of children. There were no significant differences according to the type of iPPSD or patient age. CONCLUSION: Our work shows for the first time that digestive manifestations, including constipation, occur frequently in children followed for iPPSD, suggesting a potential role of Gsα and G protein receptors in the digestive tract. It is well known that constipation and digestive symptoms alter quality of life. Early management is therefore essential to improve the quality of life of children followed for iPPSD. Our data need to be confirmed on a larger cohort.

X-linked hypophosphataemia.

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.

Long-acting growth hormone in the management of GHD in France.

Approximately 10,000 children in France with growth hormone deficiency (GHD) are being administered daily recombinant human growth hormone (rhGH). Although this treatment has long proved efficient for restoring children's growth and metabolism, daily injections of rhGH have a few limitations, such as difficulties in terms of adherence to treatment, which may compromise growth during childhood but also metabolism in adulthood. In addition to the disease burden and besides the adherence hurdles, the obligations related to daily injection have a negative impact on the quality of life of patients and their families. The hypothesis that injections administered at intervals of 1 week, or even 1 month, could improve compliance, reduce treatment discontinuations, and optimize quality of life and therapeutic effectiveness has led to the emergence of new long-acting growth hormone (LAGH). Recent access to LAGHs (somatrogon MA) on the European and French market will likely be followed by a high demand from the families concerned and may raise questions on their effectiveness, safety, and practical use. Numerous practical and practice-related points are needed to guide prescribing physicians while many concerns are still left unresolved (treatment effectiveness or ineffectiveness endpoints, long-term effectiveness, etc.). These issues can only be addressed in the future by compiling registries and conducting long-term real-world studies.

New insights into the landscape of ALPL gene variants in patients with hypophosphatasia from the Global HPP Registry.

Hypophosphatasia (HPP) is a rare, inherited metabolic disease characterized by low tissue-nonspecific alkaline phosphatase activity due to ALPL gene variants. We describe ALPL variants from the observational, prospective, multinational Global HPP Registry. Inclusion in the analysis required a diagnosis of HPP, low serum ALP activity, and ≥1 ALPL variant. Of 1176 patients enrolled as of September 2022, 814 met inclusion criteria in Europe (48.9%), North America (36.7%), Japan (10.2%), Australia (2.6%), and elsewhere (1.6%). Most patients (74.7%) had 1 ALPL variant; 25.3% had ≥2 variants. Nearly all patients (95.6%) had known disease-causing variants; 4.4% had variants of uncertain significance. Disease-causing variants were predominantly missense (770/1556 alleles). The most common variants were c.571G>A (102/1628 alleles), c.1250A>G (66/1628 alleles), and c.1559del (61/1628 alleles). Variant profiles were generally consistent, except in Japan, where a higher proportion of patients (68.7%) had ≥2 ALPL variants, likely because more had disease onset before age 6 months (53.0% vs. 10.1%-23.1% elsewhere). Frameshift mutations (61/164 alleles) and inframe deletions (7/164 alleles) were more common in Japan. Twenty-three novel variants were discovered, each in a single geographic region, predominantly Europe. Analyses confirmed previously known ALPL variants, identified novel variants, and characterized geographic variation in frequency and type of ALPL variants in a large population.

Improved Oral Health in Adults with X-Linked Hypophosphatemia Treated with Burosumab.

CONTEXT: X-linked hypophosphatemia (XLH) is a rare genetic bone disease affecting both children and adults, with oral manifestations such as spontaneous dental infections. The main treatments for XLH are conventional treatment (CT) with oral phosphate salts and active vitamin D supplementation, and burosumab, an antibody targeting Fibroblast Growth Factor 23 (FGF23). While the beneficial effect of CT on oral manifestations is established, the effect of burosumab on oral health is unknown, especially in adults. OBJECTIVE: We aimed to compare the oral health (number of missing or endodontically treated teeth and presence of periodontal disease) and incidence of endodontic infections of adult patients with XLH according to their treatment's modalities (no treatment, CT, or burosumab). METHODS: This was achieved through a single-center, retrospective analysis of oral health data from 44 patients who had undergone dental monitoring for at least 6 months. RESULTS: Oral health varied according to the proportion of their adult life spent under treatment for XLH and the incidence of dental infections during follow-up was influenced by the type of treatment received. There was a 55.9% reduction of infections during CT and an 86.4% reduction during burosumab treatment compared to periods with no treatment (P < 0.0001). Comparing treatment and non-treatment periods within the same patient showed a strong association between burosumab treatment and decreased infection incidence (0.006 vs 0.09 infection per month, P<0.01). CONCLUSIONS: We observed that adults with XLH treated with burosumab developed fewer endodontic infections during dental follow-up than patients who were untreated or received CT.

High prevalence of hypercalcitoninemia in a large cohort of adult and paediatric patients with PTH resistance syndromes.

BACKGROUND: Pseudohypoparathyroidism (PHP) refers to a group of rare hereditary disorders associated with resistance to parathormone (PTH) and other hormones now termed inactivating PTH/PTHrP disorders (iPPSD). Hypercalcitoninemia has been seldom reported in small series. Our aim was to investigate the characteristics of hypercalcitoninemia in paediatric and adult patients with PHP/iPPSD. METHODS: We retrospectively collected data from two cohorts from two European Endocrinology tertiary centers: the paediatric cohort comprised 88 children with available calcitonin (CT) measurements; the adult cohort included 43 individuals with simultaneous CT and PTH measurements. RESULTS: In the paediatric cohort 65.9% had hypercalcitoninemia (median CT 15 ng/L); in the adult cohort 53.5% (mean CT 21.6 ng/L). There was no difference between CT in paediatric and adult population; we observed stable CT levels over a median follow-up of 134.5 months in adults. Notably, no correlations were detected between CT and PTH levels. Other etiologies of hypercalcitoninemia were excluded, adult patients underwent regular thyroid ultrasound (US) to screen for medullary thyroid cancer (MTC). We performed 20 calcium stimulation tests in adult patients. While there was a significant difference in basal and peak CT between our patients, healthy subjects and subjects with MTC, there was no difference with patients with C-cell hyperplasia. CONCLUSIONS: This study underscores the common occurrence of hypercalcitoninemia in both paediatric and adult PHP/iPPSD patients, in particular with subtypes iPPSD2-iPPSD3. Furthermore, these patients show an hyperresponsiveness to calcium stimulation test falling between healthy subjects and patients with MTC. These findings contribute into the understanding of CT dynamics in the context of PHP/iPPSD.

Lessons from prospective longitudinal follow-up of a French APECED cohort.

BACKGROUND: APECED syndrome is a rare disease caused by biallelic mutations of the AIRE gene, usually presenting with the triad "hypoparathyroidism-adrenal failure-chronic mucocutaneous candidiasis (CMC)" and non-endocrine manifestations. The aim of this study was to determine the molecular profile of the AIRE gene, the prevalence of rare manifestations and to characterize immunological disturbances in a French cohort. PATIENTS AND METHODS: A national, multicenter prospective observational study to collect genetic, clinical, biological and immunological data (NCT03751683). RESULTS: 25 patients (23 families) were enrolled. Eleven distinct AIRE variants were identified, two of which were not previously reported: an intronic variant, c.653-70G > A, and a c.1066del (p.Arg356GlyfsX22) variant (exon 9). The most common was the Finnish variant c.769C > T (16 alleles), followed by the variant c.967_979del13 (15 alleles), which seemed associated with a less severe phenotype. 17/25 patients were homozygote. The median number of clinical manifestations was seven; 19/25 patients presented with the hypoparathyroidism-adrenal failure-CMC triad, 8/13 showed pulmonary involvement, 20/25 had ectodermal dystrophy, 8/25 had malabsorption, and 6/23 had asplenia. Fifteen out of 19 patients had NK cell lymphopenia with an increase in CD4+ and CD8+ T lymphocytes and an age-dependent alteration of B lymphocyte homeostasis compared with matched controls (p < 0.001), related to the severity of the disease. All tested sera (n = 18) were positive for anti-interferon-α, 15/18 for anti-interleukin-22 antibodies, and 13/18 for anti-interleukin-17F antibodies, without clear phenotypic correlation other than with CMC. CONCLUSION: This first prospective cohort showed a high AIRE genotype variability, with two new gene variants. The prevalence of potentially life-threatening non-endocrine manifestations, was higher with systematic screening. These manifestations could, along with age-dependent B-cell lymphopenia, contribute to disease severity. Systematic screening for all the manifestations of the syndrome would allow earlier diagnosis, supporting vaccination, and targeted therapeutic approaches.

Orthodontic treatment in children and adolescent patients with X-linked hypophosphatemia: A case-control study.

OBJECTIVES: X-linked hypophosphatemia (XLH) is a rare genetic disease that disturbs bone and teeth mineralization. It also affects craniofacial growth and patients with XLH often require orthodontic treatment. The aim of this study was to describe changes in the dental health of XLH children during orthodontic treatment compared with those in matched controls undergoing similar orthodontic procedures. MATERIALS AND METHODS: For this retrospective case-control study, we included all individuals less than 16 years old diagnosed with XLH, orthodontically treated in our centre from 2016 to 2022 and pair-matched them to patients with no chronic or genetic conditions. Clinical and radiological parameters concerning their malocclusion, craniofacial discrepancy and the characteristics and iatrogenic effects of their orthodontic treatment were analysed. RESULTS: Fifteen XLH patients (mean age: 11.3 ± 2.1), pair-matched to 15 control patients were included. Orthodontic treatment was successfully conducted in XLH patients with slightly shorter duration and similar iatrogenic effects as in the control group, except for the occurrence of dental abscess during and after orthodontic tooth movement. XLH patients did not show more relapse than the controls. CONCLUSION: Despite the presence of oral manifestations of XLH such as spontaneous abscesses, XLH patients can undergo orthodontic treatment with no obvious additional iatrogenic effects.

Effectiveness of asfotase alfa for treatment of adults with hypophosphatasia: results from a global registry.

BACKGROUND: Hypophosphatasia (HPP) is a rare inherited disease caused by deficient activity of tissue-nonspecific alkaline phosphatase. Many adults with HPP have a high burden of disease, experiencing chronic pain, fatigue, limited mobility, and dental issues, contributing to decreased health-related quality of life (HRQoL). HPP may be treated with the enzyme replacement therapy asfotase alfa though real-world data in adults are limited. This analysis was conducted to assess the clinical effectiveness of asfotase alfa among adults in the Global HPP Registry. METHODS: The Global HPP Registry is an observational, prospective, multinational study. Adults ≥ 18 years of age were included in this analysis if they had serum alkaline phosphatase (ALP) activity below the age- and sex-adjusted reference ranges, and/or ALPL variant(s), and received asfotase alfa for ≥ 6 months. Mobility was assessed with the 6-Minute Walk Test (6MWT), and patient-reported outcomes tools were used to assess pain (Brief Pain Inventory-Short Form), quality of life (36-item Short Form Health Survey, version 2 [SF-36v2]), and disability (Health Assessment Questionnaire-Disability Index) at multiple time points from baseline through Month 36. Data were collected as per usual standard of care; patients may not have contributed data at all time points. RESULTS: A total of 190 patients met the inclusion criteria. For patients with ≥ 1 follow-up measurement, the mean distance achieved on 6MWT increased from 404 m (range 60-632 m) at baseline (n = 31) to 484 m at Month 12 (range 240-739 m; n = 18) and remained above baseline through Month 36 (n = 7). Improvements in mean self-reported pain severity scores ranged from - 0.72 (95% CI: - 1.23, - 0.21; n = 38) to - 1.13 (95% CI: - 1.76, - 0.51; n = 26) and were observed at all time points. Improvements in the Physical Component Summary score of SF-36v2 were achieved by Month 6 and sustained throughout follow-up. There was a trend toward improvement in the Mental Component Summary score of SF-36v2 at most time points, with considerable fluctuations from Months 12 (n = 28) through 36 (n = 21). The most frequent adverse events were injection site reactions. CONCLUSIONS: Adults with HPP who received asfotase alfa for ≥ 6 months experienced improvements in mobility, physical function, and HRQoL, which were maintained over 3 years of follow-up. REGISTRATION: NCT02306720; EUPAS13514.

Reference values for serum calcium in neonates should be established in a population of vitamin D-replete subjects.

INTRODUCTION: Serum calcium is frequently measured during the neonatal period, and is known to be influenced by the vitamin D status. We hypothesized that the 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 two 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% confidence interval (CI) for serum calcium 1) in our whole population of 1002 neonates, 2) in neonates with a cord blood 25OHD concentration ≥ 30 nmol/L, and 3) 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<0.001) 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.

Serum calcium normal range in 1000 term newborns.

INTRODUCTION: Serum calcium rapidly declines at birth because of the sudden interruption of the maternal-fetal calcium influx. Several factors are known to influence serum calcium in the first days of life, including circulating concentrations of maternal vitamin D. Objective was to establish the normal range variations of neonatal serum calcium according to the French current vitamin D supplementation during pregnancy, i.e. 100,000 IU of cholecalciferol during the third trimester. METHODS: We included in our prospective cohort study 1002 mother-newborn dyads from, with recruitments from April 2012 to July 2014 in France, in two recruiting centers located in Paris neighborhoods. RESULTS: Total serum calcium at 3 days of life in neonates varied from 2.06 to 2.73 mmol/L [2.5 and 97.5 percentiles], with a mean of 2.45 mmol/L. Serum calcium was similar between babies born from vitamin D supplemented mothers and those born from the non-supplemented ones. Univariate and multivariable analyses demonstrated the importance of maternal and cord blood 25(OH)D concentrations for newborn serum calcium maintenance. CONCLUSION: We established that the expected serum calcium in neonates ranges between 2.06 and 2.73 mmol/L which is significantly wider than the adult range. This finding should help physicians in the diagnosis of hypo- or hypercalcemia. In addition, our study supports the importance of vitamin D supplementation and 25(OH)D status for neonatal serum calcium maintenance.

Developments in the Management of Growth Hormone Deficiency: Clinical Utility of Somapacitan.

Growth hormone (GH) replacement therapy for growth hormone deficiency (GHD) in children and adults has for over 25 years, until recently, been administered as daily injections. This daily treatment regimen often incurs a burden to patients and caregivers, leading to high rates of non-adherence and, consequently, decreased treatment efficacy outcomes. To address this shortcoming, long-acting growth hormones (LAGHs) have been developed with the aim of reducing the burden of daily injections, thereby potentially improving treatment adherence and outcomes. Somapacitan (Sogroya®) (Novo Nordisk, Bagsværd, Denmark) is a LAGH currently approved for the treatment of adult and childhood GHD (AGHD and CGHD, respectively) in several countries. Other LAGHs, such as somatrogon (Ngenla®) (Pfizer, New York, United States) and lonapegsomatropin/TransCon GH (Skytrofa®) (Ascendis Pharma, Copenhagen, Denmark), are also currently approved and available for the treatment of CGHD in several countries. In this review, we will consider the method of protraction, pharmacokinetics (PK) and pharmacodynamics (PD), efficacy, and safety results of somapacitan in adult and pediatric trials and how these characteristics differ from those of the other aforementioned LAGHs. Additionally, the administration of somapacitan and timing of measurement of serum insulin-like growth factor-I (IGF-I) levels are summarized. Information on administration, advice on missed doses, and clinical guidelines are discussed, as well as identifying which patients are suitable for somapacitan therapy, and how to monitor and adjust dosing whilst on therapy.

A patient-centred and multi-stakeholder co-designed observational prospective study protocol: Example of the adolescent experience of treatment for X-linked hypophosphataemia (XLH).

The importance of patient centricity and keeping the patient at the heart of research design is now well recognised within the healthcare community. The involvement of patient, caregiver and clinician representatives in the study design process may help researchers to achieve this goal and to ensure robust and meaningful data generation. Real-world data collection allows for a more flexible and patient-centred research approach for gaining important insights into the experience of disease and treatments, which is acutely relevant for rare diseases where knowledge about the disease is more likely to be limited. Here, we describe a practical example of a patient-centric, multi-stakeholder approach that led to the co-design of a prospective observational study investigating the lived experience of adolescents with the rare disease, X-linked hypophosphataemia. Specifically, we describe how the knowledge and expertise of a diverse research team, which included expert physicians, research and technology specialists, patients and caregivers, were applied in order to identify the relevant research questions and to ensure the robustness of the study design and its appropriateness to the population of interest within the context of the current clinical landscape. We also demonstrate how a structured patient engagement exercise was key to informing the selection of appropriate outcome measures, data sources, timing of data collection, and to assessing the feasibility and acceptability of the proposed data collection approach.

Proposed diagnostic criteria for the diagnosis of hypophosphatasia in children and adolescents: results from the HPP International Working Group.

Hypophosphatasia (HPP) is a rare inborn error of metabolism that presents variably in both age of onset and severity. HPP is caused by pathogenic variants in the ALPL gene, resulting in low activity of tissue nonspecific alkaline phosphatase (TNSALP). Patients with HPP tend have a similar pattern of elevation of natural substrates that can be used to aid in diagnosis. No formal diagnostic guidelines currently exist for the diagnosis of this condition in children, adolescents, or adults. The International HPP Working Group is a comprised of a multidisciplinary team of experts from Europe and North America who have expertise in the diagnosis and management of patients with HPP. This group reviewed 93 papers through a Medline, Medline In-Process, and Embase search for the terms "HPP" and "hypophosphatasia" between 2005 and 2020 and that explicitly address either the diagnosis of HPP in children, clinical manifestations of HPP in children, or both. Two reviewers independently evaluated each full-text publication for eligibility and studies were included if they were narrative reviews or case series/reports that concerned diagnosis of pediatric HPP or included clinical aspects of patients diagnosed with HPP. This review focused on 15 initial clinical manifestations that were selected by a group of clinical experts.The highest agreement in included literature was for pathogenic or likely pathogenic ALPL variant, elevation of natural substrates, and early loss of primary teeth. The highest prevalence was similar, including these same three parameters and including decreased bone mineral density. Additional parameters had less agreement and were less prevalent. These were organized into three major and six minor criteria, with diagnosis of HPP being made when two major or one major and two minor criteria are present.