Clinical practice guidelines for paediatric X-linked hypophosphataemia in the era of burosumab.

X-linked hypophosphataemia (XLH), the most common inherited form of rickets, is caused by a PHEX gene mutation that leads to excessive serum levels of fibroblast growth factor 23 (FGF23). This leads to clinical manifestations such as rickets, osteomalacia, pain, lower limb deformity and overall diminished quality of life. The overarching aims in the management of children with XLH are to improve quality of life by reducing overall burden of disease, optimise an individual's participation in daily activities and promote normal physical and psychological development. Burosumab, a monoclonal antibody targeting FGF23, has been shown to improve biochemistry, pain, function and radiological features of rickets in children with XLH and has transformed management of XLH around the world. Burosumab has been recently approved for clinical use in children with XLH in Australia. This manuscript outlines a clinical practice guideline for the use of burosumab in children with XLH to assist local clinicians, encourage consistency of management across Australia and suggest future directions for management and research. This guideline also strongly advocates for all patients with XLH to have multidisciplinary team involvement to ensure optimal care outcomes and highlights the need to consider other aspects of care for XLH in the era of burosumab, including transition to adult care and the effective coordination of care between local health-care providers and specialist services.

Peri-operative steroid management in the paediatric population.

BACKGROUND: Patients with adrenal insufficiency are at risk of adrenal crisis, a potentially life-threatening emergency in the peri-operative period due to their attenuated ability to mount a cortisol response. There is a lack of standardization regarding peri-operative stress-dose glucocorticoids in paediatric clinical practice with the absence of agreed protocols. For the individual patient, the risk of adrenal crisis must be weighed against the potential adverse clinical outcomes associated with unnecessary or supra-physiologic glucocorticoid dosing in susceptible patients. Specific clinical concerns in the paediatric population include osteopenia, growth restriction and increased risk of cardiovascular disease in adulthood. This review aimed to identify and evaluate available literature in the field of peri-operative stress-dose glucocorticoids. METHODS: A comprehensive literature search was conducted to construct a narrative review. RESULTS: The outcome of this review identified that paediatric patients, unlike adults, do not show a graded response to surgical stress with implications for glucocorticoid stress dose regimens for general anaesthesia and less invasive surgical procedures. The studies highlight a lack of information on physiological steroid responses to stress situations and differences in the approach to glucocorticoid replacement strategies in the paediatric population. CONCLUSION: The review identified there is a lack of high-quality paediatric-specific studies evaluating appropriate stress-dose glucocorticoid regimens in paediatric patients with or at risk of adrenal insufficiency. Further research is needed to establish clear evidence-based clinical guidelines for paediatric peri-operative practice regarding steroid stress dosing in adrenal insufficiency. Current knowledge would suggest that a balanced view of risks and benefits should be taken appropriate to the clinical context, to dictate peri-operative stress-dose glucocorticoids use that permits safe perioperative management.

In infants with sufficient vitamin D status at birth, vitamin D supplementation does not impact immune development.

BACKGROUND: Low vitamin D levels have been associated with allergic diseases. Vitamin D has potent immunomodulatory properties, but the mechanisms remain unclear. We have investigated the effect of oral vitamin D supplementation on circulating immune cell phenotypes in infants. METHOD: A double-blinded randomised controlled trial was conducted to investigate the effect of oral vitamin D supplementation (400 IU/d) on eczema and immune development. A subset of 78 infants was included in this analysis. Phenotypic analysis of immune cell subsets was performed using flow cytometry. RESULTS: Vitamin D supplementation resulted in median 25(OH)D levels of 80.5 vs 59.5 nmol/L in the placebo group at 3 months of age (P = .002) and 87.5 vs 77 nmol/L at 6 months of age (P = .08). We observed significant changes in immune cell composition from birth (cord blood) to 6 months of age. Vitamin D supplementation did not impact these changes, nor did immune cell composition correlate with plasma 25(OH)D levels. Through exploratory analysis, we identified possible associations with eczema development and increased abundance of naïve CD4- T cells at birth, as well as associations with basophils, iNKT and central memory CD4+ T cells, and altered expression patterns of IgE receptor (FcεR1) on monocytes and dendritic cells with eczema at 6 months. CONCLUSIONS: Vitamin D supplementation in infants who were vitamin D sufficient at birth did not affect developmental changes in immune cells during the first 6 months of life. However, immune cell profiles at birth and at 6 months of age were associated with early life eczema.

Biological basis of bone strength: anatomy, physiology and measurement.

Understanding how bones are innately designed, robustly developed and delicately maintained through intricate anatomical features and physiological processes across the lifespan is vital to inform our assessment of normal bone health, and essential to aid our interpretation of adverse clinical outcomes affecting bone through primary or secondary causes. Accordingly this review serves to introduce new researchers and clinicians engaging with bone and mineral metabolism, and provide a contemporary update for established researchers or clinicians. Specifically, we describe the mechanical and non-mechanical functions of the skeleton; its multidimensional and hierarchical anatomy (macroscopic, microscopic, organic, inorganic, woven and lamellar features); its cellular and hormonal physiology (deterministic and homeostatic processes that govern and regulate bone); and processes of mechanotransduction, modelling, remodelling and degradation that underpin bone adaptation or maladaptation. In addition, we also explore commonly used methods for measuring bone metabolic activity or material features (imaging or biochemical markers) together with their limitations.

Impact of a multimodal exercise program on tibial bone health in adolescents with Development Coordination Disorder: an examination of feasibility and potential efficacy.

OBJECTIVES: Developmental coordination disorder (DCD) compromises bone health purportedly due to lower levels of physical activity. The potential of an exercise intervention to improve bone health parameters in adolescents with DCD has not previously been studied. This study thus aimed to determine the impact of a multimodal exercise intervention on bone health in this population at-risk of secondary osteoporosis. METHODS: Twenty-eight adolescents (17 male, 11 female) aged between 12-17 years (Mage=14.1) with DCD participated in a twice weekly, 13-week generalised multimodal exercise intervention. Peripheral quantitative computed tomography scans of the tibia (4% and 66%) were performed over a six month period. Generalised estimating equations were used to examine the impact of fitness measures on bone parameters over time. RESULTS: An overall improvement trend was observed for bone health, with significant increases at the 66% tibial site for bone mass (4.12% increase, dcohen=0.23, p=0.010) and cortical area (5.42% increase, η2 =12.09, p=0.014). Lower body fitness measures were significantly associated with improvements in bone health parameters, tempered by the degree of motor impairment. CONCLUSION: A multimodal exercise intervention may be effective in improving bone health of adolescents with DCD. Given the impact of motor impairments, gains may be greater over an extended period of study.

Characterisation of peripheral bone mineral density in youth at risk of secondary osteoporosis - a preliminary insight.

OBJECTIVES: To describe peripheral long bone material and structural differences in youth at risk of secondary osteoporosis across disease-specific profiles. METHODS: Upper- and lower limbs of children and adolescents were scanned at 4% distal and 66% mid-shaft sites using peripheral Quantitative Computed Tomography sub-categorised as (1) increased risk of secondary osteoporosis (neuromuscular disorders; chronic diseases; endocrine diseases; inborn errors of metabolism; iatrogenic conditions), (2) low motor competence and (3) non-affected controls. RESULTS: Children with disease-specific profiles showed a range of bone deficits compared to the control group with these predominantly indicated for neuromuscular disorders, chronic diseases and low motor competence. Deficits between upper arm and lower leg long bone parameters were different for disease-specific profiles compared to the control group. Endocortical radius, muscle area, and mid-cortical ring density were not significantly different for any disease-specific profile compared to the control group for any bone sites. CONCLUSIONS: Neuromuscular disorders, chronic diseases and low motor competence have a strong correlation to bone health for appendicular bone parameters in youth, suggesting a critical mechanical loading influence which may differ specific to disease profile. As mechanical loading effects are observed in regional bone analyses, targeted exercise interventions to improve bone strength should be implemented to examine if this is effective in reducing the risk of secondary osteoporosis in youth.

Benefits of powered standing wheelchair devices for adolescents with Duchenne muscular dystrophy in the first year of use.

AIM: Poorer physical and mental health often accompany loss of walking in Duchenne muscular dystrophy. This study assessed the impacts of powered wheelchair standing device (PWSD) use on muscle and joint pain, joint angles when standing and mental health in adolescents with Duchenne muscular dystrophy. METHODS: Fourteen adolescents and parents participated in a stepped wedge design study over 12 months. During a baseline and intervention period, adolescents described pain and mental health, and parents reported their child's mental health. Video data were collected to measure hip, knee and ankle joint angles in the preferred standing position. RESULTS: Compared with baseline and adjusting for covariates, standing wheelchair use was associated with no change in muscle or joint pain or videoed joint angles in standing. Child-reported Strengths and Difficulties total scores decreased (coefficient -3.1, 95% confidence interval -4.6, -1.5); and parent-reported Personal Adjustment and Role Skills Scale total scores increased (coefficient 7.9, 95% confidence interval 3.3-12.5). CONCLUSIONS: PWSD use was associated with maintenance of musculoskeletal status and advantages to mental health. Long-term observations are necessary to improve understanding of how to support wellbeing in adolescents with Duchenne muscular dystrophy.

Global consensus on nutritional rickets: Implications for Australia.

In 2016, a global consensus on the prevention, diagnosis and management of nutritional rickets was published. The bone and mineral working group of the Australasian Paediatric Endocrine Group provides a summary and highlights differences to previous Australian and New Zealand (ANZ) guidelines on vitamin D deficiency and their implications for clinicians. Key points are: (i) The International Consensus document is focused on nutritional rickets, whereas the ANZ guidelines were focused on vitamin D deficiency. (ii) Definitions for the interpretation of 25-hydroxy vitamin D (25OHD) levels do not differ between statements. (iii) The global consensus recommends that routine 25OHD screening should not be performed in healthy children and recommendations for vitamin D supplementation are not based solely on 25OHD levels. The Australasian Paediatric Endocrine Group bone and mineral working group supports that screening for vitamin D deficiency should be restricted to populations at risk. (iv) Recommendations from the global consensus for vitamin D dosages for the therapy of nutritional rickets (diagnosed based on history, physical examination, biochemical testing and a confirmation by X-rays) are higher than in ANZ publications. (v) The global consensus recommends the implementation of public health strategies such as universal supplementation with vitamin D from birth to 1 year of age and food fortification. We conclude that updated global recommendations for therapy of nutritional rickets complement previously published position statements for Australia and New Zealand. Screening, management and the implementation of public health strategies need to be further explored for Australia.

Direct infant UV light exposure is associated with eczema and immune development.

BACKGROUND: Suboptimal vitamin D levels during critical periods of immune development have emerged as an explanation for higher rates of allergic diseases associated with industrialization and residing at higher latitudes. OBJECTIVE: We sought to determine the effects of early postnatal vitamin D supplementation on infant eczema and immune development. METHODS: By using a double-blind randomized controlled trial, newborn infants were randomized to receive vitamin D supplementation (400 IU/d) or a placebo until 6 months of age. Some infants also wore personal UV dosimeters to measure direct UV light (290-380 nm) exposure. Infant vitamin D levels were measured at 3 and 6 months of age. Eczema, wheeze, and immune function outcomes were assessed at 6 months of age. RESULTS: At 3 (P < .01) and 6 (P = .02) months of age, vitamin D levels were greater for the vitamin D-supplemented group than the placebo group, but there was no difference in eczema incidence between groups. Infants with eczema were found to have had less UV light exposure (median, 555 Joules per square meter [J/m2; interquartile range, 322-1210 J/m2]) compared with those without eczema (median, 998 J/m2 [interquartile range, 676-1577 J/m2]; P = .02). UV light exposure was also inversely correlated with IL-2, GM-CSF, and eotaxin production to Toll-like receptor ligands. CONCLUSION: This study is the first to demonstrate an association between greater direct UV light exposures in early infancy with lower incidence of eczema and proinflammatory immune markers by 6 months of age. Our findings indicate that UV light exposure appears more beneficial than vitamin D supplementation as an allergy prevention strategy in early life.

Endocrine and metabolic consequences due to restrictive carbohydrate diets in children with type 1 diabetes: An illustrative case series.

Low carbohydrate diets for the management of type 1 diabetes have been popularised by social media. The promotion of a low carbohydrate diet in lay media is in contrast to published pediatric diabetes guidelines that endorse a balanced diet from a variety of foods for optimal growth and development in children with type 1 diabetes. This can be a source of conflict in clinical practice. We describe a series of 6 cases where adoption of a low carbohydrate diet in children impacted growth and cardiovascular risk factors with potential long-term sequelae. These cases support current clinical guidelines for children with diabetes that promote a diet where total energy intake is derived from balanced macronutrient sources.

Please Don't Move-Evaluating Motion Artifact From Peripheral Quantitative Computed Tomography Scans Using Textural Features.

Most imaging methods, including peripheral quantitative computed tomography (pQCT), are susceptible to motion artifacts particularly in fidgety pediatric populations. Methods currently used to address motion artifact include manual screening (visual inspection) and objective assessments of the scans. However, previously reported objective methods either cannot be applied on the reconstructed image or have not been tested for distal bone sites. Therefore, the purpose of the present study was to develop and validate motion artifact classifiers to quantify motion artifact in pQCT scans. Whether textural features could provide adequate motion artifact classification performance in 2 adolescent datasets with pQCT scans from tibial and radial diaphyses and epiphyses was tested. The first dataset was split into training (66% of sample) and validation (33% of sample) datasets. Visual classification was used as the ground truth. Moderate to substantial classification performance (J48 classifier, kappa coefficients from 0.57 to 0.80) was observed in the validation dataset with the novel texture-based classifier. In applying the same classifier to the second cross-sectional dataset, a slight-to-fair (κ = 0.01-0.39) classification performance was observed. Overall, this novel textural analysis-based classifier provided a moderate-to-substantial classification of motion artifact when the classifier was specifically trained for the measurement device and population. Classification based on textural features may be used to prescreen obviously acceptable and unacceptable scans, with a subsequent human-operated visual classification of any remaining scans.

Consensus guidelines on the use of bisphosphonate therapy in children and adolescents.

Bisphosphonate therapy is the mainstay of pharmacological intervention in young people with skeletal fragility. The evidence of its use in a variety of conditions remains limited despite over three decades of clinical experience. On behalf of the Australasian Paediatric Endocrine Group, this evidence-based consensus guideline presents recommendations and discusses the graded evidence (using the GRADE system) for these recommendations. Primary bone fragility disorders such as osteogenesis imperfecta are considered separately from osteoporosis secondary to other clinical conditions (such as cerebral palsy, Duchenne muscular dystrophy). The use of bisphosphonates in non-fragility conditions, such as fibrous dysplasia, avascular necrosis, bone cysts and hypercalcaemia, is also discussed. While these guidelines provide an evidence-based approach where possible, further research is required in all clinical applications in order to strengthen the recommendations made.

Randomised controlled trial of daily versus stoss vitamin D therapy in Aboriginal children.

AIM: The prevalence of vitamin D deficiency has risen in countries with a high ultraviolet index and sunny environment such as Australia. There is lack of information on vitamin D status and best possible therapy in Australian Aboriginal children. We aim to (i) describe the vitamin D status in an opportunistic sample of Aboriginal children in Western Australia and (ii) compare the efficacy of oral daily vitamin D with oral stoss vitamin D therapy in this sample. METHOD: Participants were recruited from a metropolitan area (31' S) and a rural area (17' S). Those with a 25(OH)D level less than 78 nmol/L were randomised to receive daily or stoss vitamin D therapy with follow-up at 4-6 months and 9-12 months. Biochemical and clinical parameters such as 25(OH)D, alkaline phosphatase, calcium and sun exposure were collected. RESULTS: Seventy-three participants were enrolled (61 from a metropolitan and 12 from a rural area). 25(OH)D levels were greater than 78 nmol/L in 9/12 (75%) participants in the rural group and 21/61 (34%) in the metropolitan group. 25(OH)D levels were less than 78 nmol/L in 43/73 (59%) participants. Of these, 34/43 (79%) were insufficient (50-78 nmol/L), 8/43 (19%) mildly deficient (27.5-50 nmol/L) and 1/43 (2%) deficient (<27.5 nmol/L). Daily vitamin D therapy had a higher average increase in 25(OH)D levels from baseline than stoss therapy; however, this was not significant. CONCLUSION: Vitamin D insufficiency is common in Aboriginal children of Western Australia and stoss therapy is a safe alternative to daily vitamin D therapy but requires further evaluation of timing and doses.

Retrospective Examination of Peripubertal Return for Patients of Western Australia's Gender Diversity Service.

Purpose: Children far in advance of pubertal development may be deferred from further assessment for gender-affirming medical treatment until nearer puberty. It is vital that returning peripubertal patients are seen promptly to ensure time-sensitive assessment and provision of puberty suppression treatment where appropriate. This study investigates (1) how many referrals to the Child and Adolescent Health Service Gender Diversity Service at Perth Children's Hospital are deferred due to prepubertal status; and (2) how many deferred patients return peripubertally. Methods: A retrospective review of all closed referrals to the service was conducted to determine the frequency of prepubertal deferral and peripubertal re-referral. Results: Of 995 referrals received (2014 to 2020), 552 were closed. The reason for closure was determined for 548 referrals (99.3%). Prepubertal status was the second-most frequent reason for closure, and the most frequent for birth-registered males. Twenty-five percent of all deferred prepubertal patients returned peripubertally, before audit closure. A greater return frequency (55.6%) was estimated for those older than 13 years at audit closure. Conclusion: High rates of prepubertal referral indicate the importance of pediatric gender services in providing information, advice, and reassurance to concerned families. With increasing service demand, high rates of return peripubertally have implications for service planning to ensure that returning peripubertal patients are seen promptly for time-sensitive care. Frequency of peripubertal re-referral cannot, however, speak to the stability of trans identity or gender incongruence from childhood to adolescence. Clinics advising prepubertal deferral must proactively plan to ensure that sufficient clinical resources are reserved for this purpose.

Reidentification With Birth-Registered Sex in a Western Australian Pediatric Gender Clinic Cohort.

Importance: Some young people who identify as transgender and seek gender-affirming medical care subsequently reidentify with their sex registered at birth. Evidence regarding the frequency and characteristics of this experience is lacking. Objective: To determine the frequency of reidentification and explore associated characteristics in a pediatric gender clinic setting. Design, Setting, and Participants: This retrospective cohort study examined all referrals to the Child and Adolescent Health Service Gender Diversity Service at Perth Children's Hospital between January 1, 2014, and December 31, 2020. The Gender Diversity Service is the sole statewide specialist service in Western Australia that provides children and adolescents up to age 18 years with multidisciplinary assessment, information, support, and gender-affirming medical care. All closed referrals for this study were audited between May 1, 2021, and August 8, 2022. Exposure: Reidentification with birth-registered sex. Main Outcomes and Measures: The number of referrals closed due to reported reidentification with birth-registered sex was determined, as well as descriptives and frequencies of patient demographics (age, birth-registered sex), informant source, International Statistical Classification of Diseases, Tenth Revision gender-related diagnoses, pubertal status, any gender-affirming medical treatment received, and whether subsequent re-referrals were received. Results: Of 552 closed referrals during the study period, a reason for closure could be determined for 548 patients, including 211 birth-registered males (mean [SD] age, 13.88 [2.00] years) and 337 birth-registered females (mean [SD] age, 15.81 [2.22] years). Patients who reidentified with their birth-registered sex comprised 5.3% (29 of 548; 95% CI, 3.6%-7.5%) of all referral closures. Except for 2 patients, reidentification occurred before or during early stages of assessment (93.1%; 95% CI, 77.2%-99.2%). Two patients who reidentified with their birth-registered sex did so following initiation of puberty suppression or gender-affirming hormone treatment (1.0% of 196 patients who initiated any gender-affirming medical treatment; 95% CI, 0.1%-3.6%). Conclusions and Relevance: These findings from a pediatric gender clinic audit indicate that a small proportion of patients, and a very small proportion of those who initiated medical gender-affirming treatment, reidentified with their birth-registered sex during the study period. Longitudinal follow-up studies, including qualitative self-report, are required to understand different pathways of gender identity experience.

Vitamin D and health in pregnancy, infants, children and adolescents in Australia and New Zealand: a position statement.

• The recommended level for serum 25-hydroxyvitamin D (25(OH)D) in infants, children, adolescents and during pregnancy and lactation is ≥ 50 nmol/L. This level may need to be 10-20 nmol/L higher at the end of summer to maintain levels ≥ 50 nmol/L over winter and spring. • Sunlight is the most important source of vitamin D. The US recommended dietary allowance for vitamin D is 600 IU daily in children aged over 12 months and during pregnancy and lactation, assuming minimal sun exposure. • Risk factors for low vitamin D are: lack of skin exposure to sunlight, dark skin, southerly latitude, conditions affecting vitamin D metabolism and storage (including obesity) and, for infants, being born to a mother with low vitamin D and exclusive breastfeeding combined with at least one other risk factor. • Targeted measurement of 25(OH)D levels is recommended for infants, children and adolescents with at least one risk factor for low vitamin D and for pregnant women with at least one risk factor for low vitamin D at the first antenatal visit. • Vitamin D deficiency can be treated with daily low-dose vitamin D supplements, although barriers to adherence have been identified. High-dose intermittent vitamin D can be used in children and adolescents. Treatment should be paired with health education and advice about sensible sun exposure. Infants at risk of low vitamin D should be supplemented with 400 IU vitamin D3 daily for at least the first year of life. • There is increasing evidence of an association between low vitamin D and a range of non-bone health outcomes, however there is a lack of data from robust randomised controlled trials of vitamin D supplementation.

The Natural History of Symptomatic Fractures in Children and Adolescents with Osteogenesis Imperfecta Type 1: A Cohort Study from Western Australia.

The fracture experience of children and adolescents with osteogenesis imperfecta (OI) type 1 is not well described in the literature. We present data on symptomatic long bones and axial skeleton fractures of all patients aged 0 to 18 years with OI type 1 seen at a specialized bone clinic in Western Australia in the period 2008 to 2020 using a retrospective chart review method. The cohort consisted of 44 patients (21 males, 23 females). Median (interquartile range [IQR]) age was 11.3 (6.2 to 17) years, giving a total of 520 patient-years in the study during which 197 fractures were experienced. The mean fracture rate was 379 fractures per 1000 patient-years (95% confidence interval [CI]: 310 to 440); however, the experience for fractures varied from ≤1 fracture in 23% (n = 10) to two to 20 in 77% (n = 34) of the cohort. Twenty-one patients (48.5%) received bisphosphonates during the study period. In logistic regression, age, but not sex or family history of OI, was a significant predictor of fracture risk. The highest total fracture rate was observed in the age group 0 to <3 years at 469 fractures/1000 patient-years, which declined to 140 fractures/1000 patient-years in the age group 15 to 18 years. The lower limbs were the site of 49.7% of all fractures. The highest rate for lower limb fracture was in the age group 0 to <3 years at 331 fractures/1000 patient-years, decreasing to 0 fractures/1000 patient-years in the age group 15 to 18 years. Upper limb fracture rates increased from 100 fractures/1000 patient-years in the 0 to <3 years age group to 307 fractures/1000 patient-years in the 9 to <12 years age group and then declining to 70 fractures/1000 years in the 15 to 18 years age group. In pediatric patients with OI type 1, fracture risk is highest in early life, especially in the lower limbs. Multidisciplinary care of children with OI should have a particular focus on strategies to prevent these fractures. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Prevalence and characteristics of paediatric X-linked hypophosphataemia in Australia and New Zealand: Results from the Australian and the New Zealand Paediatric Surveillance Units survey.

BACKGROUND: X-linked hypophosphataemia (XLH) is the most common heritable form of rickets. Prevalence data varies across the literature between 1 in 20,000 and 1 in 200,000 per population. METHODS: Australian and New Zealand Paediatric Surveillance Units collected cross-sectional data from paediatricians on existing cases to estimate prevalence and characteristics of paediatric XLH in Australia and New Zealand. RESULTS: Seventy-five cases in Australia and 18 cases in New Zealand were identified. Estimated minimum prevalence based on these cases was 1.33 (1.04-1.66) per 100,000 and 1.60 per 100,000 (95%CI 0.97-2.58) in Australia and New Zealand respectively, with actual prevalence likely higher due to incomplete ascertainment. Despite a family history in most cases, delayed diagnosis was common, with 49 % diagnosed after 2 years of age. Delayed diagnosis was more common in sporadic versus familial cases. Most common clinical characteristics included leg bowing (89 %), bone and joint pain (68 %), abnormal gait (57 %) and short stature (49 %). There was a significant burden of orthopaedic disease and surgeries and a high rate of complications of nephrocalcinosis and hyperparathyroidism (32 % and 20 % respectively). Additionally, while guidelines stress the importance of multidisciplinary care, many did not have access to recommended health professionals, with only 3 % seeing a psychologist and 68 % seeing a dentist. This is despite the high psychological burden of XLH and a significant proportion (41 %) of this cohort having dental issues (tooth abscess, dental capping, tooth extraction). There were two cases from NZ without data available. Of the 91 cases with data collected, 46 % were on burosumab therapy. Consistent with clinical trials, those on burosumab had a higher serum phosphate levels (p < 0.001) at most recent follow-up. Three cases reported cancellation of orthopaedic surgery due to improvement in lower limb deformity after commencement of burosumab. CONCLUSION: These data describe the multisystem burden of disease for children with XLH with care impacted by delayed diagnosis and a lack of access to many health professionals, especially psychological support.

Sterile abscess formation associated with depot leuprorelin acetate therapy for central precocious puberty.

We describe a case of an 8 year old girl with central precocious puberty. She was commenced on 3 monthly intramuscular depot Leuprorelin acetate therapy, as a result of which she developed sterile abscesses. She was converted to daily subcutaneous Leuprorelin acetate therapy with no recurrence of the abscesses. The possible mechanisms for this reaction are described in the article.