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.

Outcomes of Zoledronic Acid Use in Paediatric Conditions

INTRODUCTION

Limited evidence is available concerning experience with use of zoledronic acid (ZA) and treatment for conditions other than primary bone fragility.

MATERIALS AND METHODS

A retrospective review of all Royal Children Hospital patients who had been administered at least 1 dose of intravenous ZA from 2002 to 2015 was undertaken.

RESULTS

The audit included 309 children with 228 being treated for bone fragility conditions. Of the 228, 68 had height-adjusted lumbar spine bone mineral density Z-scores available over up to a 5-year period, and median increases were +2.0 SD (median absolute deviation = 0.9) (N = 36, p value for median increase of at least 0.5 in Z-score <0.001), for patients with osteogenesis imperfecta or other primary bone fragility disorders, +1.0 SD (0.9) (N = 14, p = 0.029), for immobility conditions, +0.5 SD (0.7) (N = 10, p = 0.399), and for glucocorticoid-induced secondary osteoporosis, +0.7 SD (0.6) (N = 8, p = 0.015). 81/309 children were treated for bone abnormality indications (e.g., avascular necrosis [AVN], fibrous dysplasia, and bone cysts). Of 39 with AVN, outcome data were available for 33, with joint integrity maintained for 24/33 from 6 to 24 months after last ZA, subjective reports (22/28) of reduced pain. Reduction in bone lesion size was seen in 2/4 patients with bone cysts within 12 months of ZA commencement.

DISCUSSION/CONCLUSION

This is the largest cohort of reported outcomes of ZA use in a paediatric population. Results demonstrate a good efficacy profile and associated improved bone density for osteoporotic conditions and stabilization of non-traumatic AVN with a low rate of joint collapse.

Risk of Fractures and Other Injuries in Children Treated with Antiseizure Medications for Epilepsy

This study aimed to investigate the prevalence of fractures and non-fracture injuries, including associated risk factors, in children with epilepsy prescribed antiseizure medications (ASM). A controlled, cross-sectional study was conducted in a hospital outpatient setting, comparing children with epilepsy prescribed ASMs with their non-epileptic siblings. Information was collected by questionnaire included history of fractures, non-fracture injuries and epilepsy, comorbidities and ASM use. 261 participants completed the questionnaire, 133 children with epilepsy (aged 10.7 ± 3.5 years, mean ± SD) and 128 siblings (10.1 ± 3.7 years). There were 49 non-seizure-related fractures in 34 ASM patients while prescribed ASMs, compared with 21 lifetime fractures in 15 controls, giving a 2.7 (95% CI 1.3-5.3, p = 0.007) times greater fracture prevalence in children treated with ASMs compared to healthy siblings. The rates of non-fracture injuries were similar across groups, except that concussion was more common in children taking ASMs (9.0% vs 1.6%, p = 0.026). Duration of ASM use and generalized tonic-clonic seizures (GTCS) were independent predictors of fractures (OR 1.55; 95% CI 1.03-2.31, p = 0.03; OR 2.50; 95% CI 1.05-5.94, p = 0.04, respectively). Fewer than 20% of participants and/or their families were aware that ASM use was related to bone health. Children with epilepsy treated with ASMs had a higher fracture prevalence than their sibling controls. Duration of ASM treatment and GTCS were associated with fracture risk. Longitudinal prospective studies are required to further explore risk and the direct impact of epilepsy on bone health.

Randomized Controlled Trial Evaluating the Use of Zoledronic Acid in Duchenne Muscular Dystrophy

CONTEXT

Patients with glucocorticoid-dependent Duchenne muscular dystrophy (DMD) have increased fracture risk and reduced bone mineral density (BMD), often precipitating mobility loss.

OBJECTIVE

To investigate use of zoledronic acid (ZA) in DMD in improving BMD.

METHODS

Two arm, parallel, randomized controlled trial, set in pediatric hospitals across Australia and New Zealand. Sixty-two (31 per arm) boys with glucocorticoid-dependent DMD between 6 and 16 years were included. Five ZA infusions (0.025 mg/kg at months 0, and 3, and 0.05 mg/kg at months 6, 12, and 18), plus calcium and vitamin D, were compared with calcium and vitamin D alone. The main outcome measures were change in lumbar spine (LS) BMD raw and Z-score by dual energy absorptiometry x-ray (DXA) at 12 and 24 months, secondary outcomes assessing mobility, fracture incidence, bone turnover, peripheral quantitative computerized (pQCT) and pain scores.

RESULTS

At 12 and 24 months, mean difference in changes of LS BMD Z-score from baseline was 1.2 SD (95% CI 0.9-1.5), higher by 19.3% (14.6-24.0) and 1.4 SD (0.9-1.9), higher by 26.0% (17.4-34.5) in ZA than control arms respectively (both P < .001). Five controls developed Genant 3 vertebral fractures, 0 in the ZA arm. Mobility, pain, and bone turnover markers were similar between arms at 12 and 24 months. Trabecular BMC and vBMD pQCT at radius and tibia were greater at 12 months in the ZA cohort than control; the evidence for this difference remained at 24 months for radius but not tibia.

CONCLUSION

ZA improved BMD in glucocorticoid-dependent DMD boys. Although the small cohort precluded demonstrable fracture benefit, improved BMD might reduce incident vertebral fracture.

Effect of Testosterone Treatment for Delayed Puberty in Duchenne Muscular Dystrophy

OBJECTIVE

To evaluate the impact of pubertal induction with testosterone on bone health, body composition, and motor function in boys with Duchenne muscular dystrophy (DMD) receiving long-term glucocorticoid.

STUDY DESIGN

A retrospective, observational, pre-post study investigating the impact of testosterone therapy on bone mass accrual, vertebral fracture incidence, body composition, motor function, and quality of life in boys with DMD. All those boys aged ≥14 years, on chronic steroid therapy, who had delayed puberty, and were receiving oral testosterone or oral and then transitioned to intramuscular testosterone, to complete virilization, were included. Prior/concomitant zoledronic acid use was included. The primary outcome was lumbar spine areal bone mineral density (BMD LS).

RESULTS

Puberty was induced, using oral testosterone undecanoate in 16 individuals, 10 of whom had transited to intramuscular testosterone at time of assessment. Median age at testosterone onset was 14.5 years (range 14-17.7). Median duration of testosterone therapy was 2.5 years (range 1.0-4.5). There was statistically significant increase in median BMD LS (0.523-0.700, p < 0.001) and median annualized percentage change of BMD LS (-1.34 to +10.08%, p < 0.001), with median Tanner stage 4 at evaluation (range 2-4). Ten of 14 assessed had no progression in vertebral fractures. Fat mass index (FMI) standard deviation score (SDS), lean body mass index (LBMI) SDS, and percentage change of FMI and LBMI were statistically unchanged. Cardiac function remained stable. Motor function in non-ambulatory individuals with Egen Klassifikation scores improved in 7 of 8.

CONCLUSION

Testosterone for delayed puberty acted as an adjunct to bisphosphonates to increase bone density and stabilize vertebral fracture in most boys with DMD.

The clinical features that contribute to poor bone health in young Australians living with cystic fibrosis: A recommendation for BMD screening

BACKGROUND

For Australians living with cystic fibrosis (CF), increased longevity means greater consideration needs to be given to long-term endocrine sequelae such as CF-related bone disease. Deficits in bone mass accrual are most likely to occur during childhood and adolescence. Current guidelines in Australia suggest repeat dual-energy X-ray absorptiometry (DXA) scans every 2 years. This study aims to stratify clinical factors that determine future bone health in the Australian CF population and use this to guide a more streamlined approach to bone health screening.

METHODS

This study was a retrospective audit of all patients diagnosed with CF who were treated at the Royal Children's Hospital Melbourne, Australia from 2000 to 2016 (n = 453). Two hundred and two patients had a DXA scan in the study period (191 with height-adjusted data) and 111 patients had more than one scan (108 with height-adjusted data). An investigation into the associations between bone mineral density (BMD) Z score and potential risk factors was conducted using DXA and historical data.

RESULTS

The main predictor of future BMD was the previous BMD Z score (p < .001). Other factors found to be determinants of BMD included nutritional status, lung function (FEV₁ ), age, history of previous fracture, oral corticosteroid use, and the number of hospital admissions. However, after adjusting for previous BMD, evidence of an association remained only with nutritional status, FEV₁ , and number of hospital admissions.

CONCLUSION

Second yearly scans may be unnecessary in children with an adequate DXA score on the initial scan who remain clinically stable. However, clinical deterioration in those whose BMD was previously normal, may require closer monitoring of bone health. We propose a guideline for the frequency of DXA monitoring in relation to clinical risk factors.

OR15-01 Blockers and Bones: Loss of Absolute Bone Mineral Density Is Common in Trans- and Gender- Diverse Adolescents Treated with GnRHa

Background: The expected pubertal accrual of bone mineral density (BMD) may be disrupted in trans and gender diverse (TGD) adolescents who undergo pubertal suppression with Gonadotropin Releasing Hormone agonists (GnRHa)1. The extent of this effect remains unclear and is confounded by varying methods used to assess BMD1.

While BMD Z-scores in GnRHa-treated TGD adolescents may be expected to decline relative to pubertal peers, this measure provides no information on actual changes in BMD. Annualised, percent change in BMD (%BMD velocity, %BMDV) provides a standardised measure of accrual or loss, but has not been reported in this context.

Aims: (1) To evaluate bone accrual or loss using %BMDV in a cohort of GnRHa-treated TGD adolescents; (2) to explore associations between baseline characteristics (BMD Z score, Vitamin D status and Tanner Stage) and %BMDV.

Methods. Retrospective 10yr audit at tertiary pediatric gender service. Bone densitometry data were collected at baseline and 12-24monthly during GnRHa. Areal BMD values and Z-scores for lumbar spine (LS) and total hip (TH) were obtained. %BMDV between baseline and final scan was calculated for LS and TH. Population data for %BMDV before and during puberty were derived from the BMD in Childhood Study2. Results are reported as mean (±SD) or mean difference (MD; 95% confidence interval).

Results. Data from 28 patients (20 transfemale; 8 transmale) who commenced GnRHa at 13.3 (±2.0) yrs and were observed over 23.2 (±11.5) mo were included. Mean (±SD) %aBMDV during GnRHa therapy was -0.66 (±4.54) %/yr for TH and +1.91 (±4.23) %/yr for LS, both substantially lower than %aBMDV in pre-pubertal population controls (~+3-4%/year). 53% of GnRHa-treated youth exhibited negative %aBMDV, indicating bone loss, at TH and/or LS. %aBMDV was lower in (i) Vitamin D deficient youth, with MD at TH (-6.07; -9.00, -3.13); and LS (-4.93; -9.56, -0.30) relative to Vitamin D sufficient peers and (ii) youth who were Tanner stage 4+ at baseline, with MD at TH (-4.1; -7.7, -0.44) and LS (-3.6; -7.2, 0.01) relative to Tanner stage 2-3 peers. Height-adjusted Z scores declined from baseline with GnRHa treatment in &gt;95% of patients and were not predictive of %aBMDV.

Conclusion. GnRHa-treated TGD adolescents in this cohort exhibited lower BMD accrual rates than pre-pubertal population controls. Over half of our cohort lost BMD, which is a significant concern in adolescence. Vitamin D deficiency and more advanced pubertal stage at GnRHa initiation were associated with greater bone loss during treatment. These data highlight the need to monitor and optimise bone health in GnRHa-treated TGD young people. We recommend routine annual densitometry and %BMDV evaluation regardless of baseline Z-scores as well as routine screening and treatment of vitamin D deficiency while on GnRHa.

References.

1.

Chew D., et al., Pediatrics, 2018. 141: p.e20173742.

2.

Zemel B.S., et al., JCEM, 2011. 96 p.3160-9.

pQCT bone geometry and strength: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe the epidemiology and concordance of bone health in a population-based sample of Australian parent-child dyads at child age 11-12 years.

DESIGN

Population-based cross-sectional study (the Child Health CheckPoint) nested between waves 6 and 7 of the Longitudinal Study of Australian Children (LSAC).

SETTING

Assessment centres in seven cities around Australia, February 2015-March 2016.

PARTICIPANTS

of all participating CheckPoint families (n=1874), bone data were available for 1222 dyads (1271 children, 50% girls; 1250 parents, 86% mothers).

OUTCOME MEASURES

Peripheral quantitative CT (pQCT) of the non-dominant leg scanned at the 4% (distal) and 66% (mid-calf) tibial sites. Stratec XCT 2000 software generated estimates of bone density, geometry and polar stress-strain index.Parent-child concordance were assessed using Pearson's correlation coefficients and multivariable linear regression models. Percentiles were determined using survey weights. Survey weights and methods accounted for LSAC's complex sampling, stratification and clustering within postcodes.

RESULTS

Concordances were greater for the geometric pQCT parameters (periosteal circumference 0.38, 95% CI 0.33 to 0.43; endosteal circumference 0.42, 95% CI 0.37 to 0.47; total cross-sectional area 0.37, 95% CI 0.32 to 0.42) than density (cortical density 0.25, 95% CI 0.19 to 0.30). Mother-child and father-child values were similar. Relationships attenuated only slightly on adjustment for age, sex and body mass index. Percentiles and concordance are presented for the whole sample and by sex.

CONCLUSIONS

There is strong parent-child concordance in bone geometry and, to a lesser extent, density even before the period of peak adolescent bone deposition. This geometrical concordance suggests that future intergenerational bone studies could consider using pQCT rather than the more commonly used dual X-ray absorptiometry (DXA).

A comparative study of quality of life, functional and bone outcomes in osteogenesis imperfecta with bisphosphonate therapy initiated in childhood or adulthood

Bisphosphonates have been used for treatment of bone fragility disorders for over 25 years to increase bone mineral density (BMD). Anecdotally, bisphosphonate-treated Osteogenesis Imperfecta (OI) has a different trajectory to the natural history of untreated OI in terms of fracture incidence, quality of life and physical function, with minimal published evidence to support this clinical observation. This study describes functional outcomes of a cohort of adults with OI, stratified according to severity and treated with intravenous bisphosphonates as children. Reported outcomes included fracture incidence before and after puberty, mobility and BMD outcomes of this cohort. The cohort was compared to adults with OI who were never treated as children. All participants completed four questionnaires: a study specific questionnaire addressing fracture and treatment history, WHOQOL-BREF (quality of life), SF-36 (musculoskeletal function) and IPAQ (physical activity), and medical records were reviewed. Fifty-two adults with OI (80% response rate) completed the questionnaires; 33 of whom were treated with bisphosphonates in childhood. The childhood treated cohort had higher lumbar spine BMD than the adult treated cohort (z-score - 0.4 at mean age 21.3 years versus -2.1 at mean age 40.9 years; p = 0.003). Pre-pubertal fracture incidence was reduced for all severities of OI in the childhood treated cohort (less severe OI, p = 0.01; more severe OI, p < 0.001), but post-pubertal fracture incidence was higher for less severe OI (p < 0.001). In less severe OI, childhood treated individuals had higher levels of physical activity (p = 0.004) and physical functioning (p = 0.01) than adult treated individuals. Incidence of scoliosis was not different between cohorts. There were no differences in quality of life scores between the two cohorts. Improvements in BMD do not appear to influence the prevalence of scoliosis. Results suggest that treatment with bisphosphonates at an earlier age improves physical activity, particularly in less severe forms of OI but may not alter quality of life.

Outcomes of standardised approach to metabolic bone disease of prematurity

AIM

To assess the current protocol of metabolic bone disease (MBD) at three Monash Health neonatal units (Melbourne, Australia).

METHODS

Retrospective audit of 171 infants born at <32 weeks' gestation over 18 months. Mean gestational age was 28.6 ± 2.1 weeks, and birthweight was 1190 ± 374 g. Risk factors of MBD include intra-uterine growth retardation (n = 33, 19.3%), maternal pre-eclampsia (n = 17, 9.9%), necrotising enterocolitis (n = 9, 5.4%) and medications like methylxanthines (94.2%; mean 54.8 days), diuretics (38.6%; mean 49.2 days) and glucocorticoids (5.3%; mean 35 days).

RESULTS

In total, 84.8% infants had an initial MBD screen (mean age 36.3 days), with 45% having repeated monitoring (mean age 71.9 days), and 14.2% had initial alkaline phosphatase levels >500 U/L, decreasing to 10.1% on follow-up. All infants received additional vitamin D supplementation of 400 IU/day, phosphate of 25.1% (n = 43) and calcium of 19.9% (n = 34). Fractures were identified from clinical documentation in 2.9% (n = 5) of infants. Stratifying into phosphate-treated and untreated groups revealed significant differences (P < 0.001) for gestational age and birthweight: 26.7 ± 1.7 weeks/918 ± 272 g for treated versus 29.2 ± 1.9 weeks/1283 ± 359 g for untreated. In the phosphate-treated group, improvement was seen in mean alkaline phosphatase (pre-treatment 467 ± 204 U/L and post-treatment 342 ± 221 U/L, P < 0.01) and mean phosphate levels (1.8 ± 0.4 vs. 2.2 ± 1.0 mmol/L, P < 0.01). Linear growth difference between phosphate-treated (n = 10) and untreated groups (n = 24) was insignificant at >6 months of age (P = 0.13), although this may reflect limited data.

CONCLUSION

Adequate first-line supplementation with vitamin D and phosphate appeared to improve biochemical markers of MBD, but given the observational nature of this study, further longitudinal/prospective studies are required to confirm these findings.

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.

Monoallelic BMP2 Variants Predicted to Result in Haploinsufficiency Cause Craniofacial, Skeletal, and Cardiac Features Overlapping Those of 20p12 Deletions

Bone morphogenetic protein 2 (BMP2) in chromosomal region 20p12 belongs to a gene superfamily encoding TGF-β-signaling proteins involved in bone and cartilage biology. Monoallelic deletions of 20p12 are variably associated with cleft palate, short stature, and developmental delay. Here, we report a cranioskeletal phenotype due to monoallelic truncating and frameshift BMP2 variants and deletions in 12 individuals from eight unrelated families that share features of short stature, a recognizable craniofacial gestalt, skeletal anomalies, and congenital heart disease. De novo occurrence and autosomal-dominant inheritance of variants, including paternal mosaicism in two affected sisters who inherited a BMP2 splice-altering variant, were observed across all reported families. Additionally, we observed similarity to the human phenotype of short stature and skeletal anomalies in a heterozygous Bmp2-knockout mouse model, suggesting that haploinsufficiency of BMP2 could be the primary phenotypic determinant in individuals with predicted truncating variants and deletions encompassing BMP2. These findings demonstrate the important role of BMP2 in human craniofacial, skeletal, and cardiac development and confirm that individuals heterozygous for BMP2 truncating sequence variants or deletions display a consistent distinct phenotype characterized by short stature and skeletal and cardiac anomalies without neurological deficits.

Growth disorders in adolescents

BACKGROUND

Growth is one of the fundamental processes of adolescent development. Careful history and examination, and relevant tar-geted investigations, can streamline the referral process, highlighting the important role of primary healthcare clinicians.

OBJECTIVE

This article will provide a guide for clinicians to categorise growth patterns in adolescents, and recognise patients who may have a growth disorder. It will assist clinicians in considering appropriate investigations, and provide guidance for when to refer the adolescent to appropriate paediatric specialists.

DISCUSSION

Causes of tall and short stature can often be distinguished on history, physical examination, and accurate pubertal staging. The height of the adolescent should always be considered in the context of their genetic potential. Physiological variants re-main the most common reason for short stature, but awareness of the features of pathological causes is critical. One of the most common presentations is maturational delay in males, and an approach to this issue is discussed.

The effect of the ketogenic diet on the developing skeleton

The ketogenic diet (KD) is a medically supervised, high fat, low carbohydrate and restricted protein diet which has been used successfully in patients with refractory epilepsy. Only one published report has explored its effect on the skeleton. We postulated that the KD impairs skeletal health parameters in patients on the KD. Patients commenced on the KD were enrolled in a prospective, longitudinal study, with monitoring of Dual-energy X-ray absorptiometry (DXA) derived bone parameters including bone mineral content and density (BMD). Areal BMD was converted to bone mineral apparent density (BMAD) where possible. Biochemical parameters, including Vitamin D, and bone turnover markers, including osteocalcin, were assessed. Patients were stratified for level of mobility using the gross motor functional classification system (GMFCS). 29 patients were on the KD for a minimum of 6 months (range 0.5-6.5 years, mean 2.1 years). There was a trend towards a reduction in lumbar spine (LS) BMD Z score of 0.1562 (p=0.071) per year and 20 patients (68%) had a lower BMD Z score at the end of treatment. While less mobile patients had lower baseline Z scores, the rate of bone loss on the diet was greater in the more mobile patients (0.28 SD loss per year, p=0.026). Height adjustment of DXA data was possible for 13 patients, with a mean reduction in BMAD Z score of 0.19 SD. Only two patients sustained fractures. Mean urinary calcium-creatinine ratios were elevated (0.77), but only 1 patient developed renal calculi. Children on the KD exhibited differences in skeletal development that may be related to the diet. The changes were independent of height but appear to be exaggerated in patients who are ambulant. Clinicians should be aware of potential skeletal side effects and monitor bone health during KD treatment. Longer term follow up is required to determine adult/peak bone mass and fracture risk throughout life.

Low vitamin D is associated with hypertension in paediatric obesity

AIM

The aim of this paper was to investigate the relationship between circulating 25-hydroxyvitamin D (25(OH)D) and cardio-metabolic risk factors in a large cohort of obese youth attending tertiary paediatric obesity services.

METHODS

We conducted a retrospective cross-sectional study. Data were retrospectively collected from all new consultations of children and adolescents attending obesity outpatient clinics between 2008 and 2011 at the two major paediatric hospitals in Melbourne, Australia. Information collected included demographics, anthropometry, blood pressure, pubertal staging, body composition and fasting serum levels of 25(OH)D, glucose, insulin, cholesterol, triglyceride, high-density lipoprotein, liver function, calcium and phosphate.

RESULTS

25(OH)D data were available in 229 patients (age 3-18 years; 116 men; mean (standard deviation) body mass index ( BMI) Z-score 2.5 (0.5) ). One hundred four (45%) participants were 25(OH)D deficient (<50 nmol/L). Lower serum 25(OH)D levels were associated with higher BMI Z-score (P-trend = 0.001), total fat mass (P-trend = 0.009), systolic (P-trend = 0.03) and diastolic blood pressures(P-trend = 0.009). In multivariable-adjusted regression analysis, 25(OH)D was significantly lower in those with elevated blood pressure after adjustment for BMI(P-trend = 0.004) or total fat mass (P-trend = 0.01).

CONCLUSION

Overweight and obese youth attending specialist obesity services have a high prevalence of vitamin D deficiency. In this population, lower levels of vitamin D were seen in those with greater adiposity, and independent of this, in those who had higher blood pressure.

Bone density assessment in a tertiary paediatric centre over 13 years: Referral patterns and limitations

AIM

This study aims to examine the referral practices for the Royal Children's Hospital (RCH) bone density service over the past 13 years and to demonstrate referral patterns and possible limitations to accessing paediatric bone densitometry.

METHODS

All patients attending the RCH Healthy Bones Unit for bone densitometry from 1 July 1999 to 30 June 2012, aged under 18 years of age, were included. Densitometry results were downloaded directly from the Hologic scanner into an Excel document. However, the referring unit and indication for referral were collected manually from either the referral card or the hospital's scanned medical records system.

RESULTS

A total of 5767 bone densitometry scans were performed over the study period on 3004 patients. The majority of referrals were made by the Endocrinology department, followed by Adolescent Medicine, Gastroenterology and Neurology. Relatively few referrals were made by general paediatrics. The most common indication for bone density test overall was eating disorders, followed by steroid use, osteogenesis imperfecta and other collagen disorders and inflammatory bowel disease. The lowest lumbar spine z-scores by indication were for cerebral palsy and other causes of immobility.

CONCLUSIONS

Multiple childhood diseases predispose to low bone density; however, paediatric bone densitometry is still underutilised and not appropriately supported by subsidies.

Geography does not limit optimal diabetes care: use of a tertiary centre model of care in an outreach service for type 1 diabetes mellitus

AIM

Young people with type 1 diabetes mellitus living in rural and regional Australia have previously been shown to have limited access to specialised diabetes services. The Royal Children's Hospital Melbourne has been running diabetes outreach clinics to Western Victoria, Australia, for over 13 years. We aim to evaluate this service by comparing the outcomes of three outreach clinics with our urban diabetes clinic at the Royal Children's Hospital Melbourne.

METHODS

We examine our tertiary, multidisciplinary team-based model of care, where visiting specialist medical staff work alongside local allied health teams. The local teams provide interim care between clinics utilising the same protocols and treatment practices as the tertiary centre. Longitudinal data encapsulating the years 2005-2010, as a cohort study with a control group, are reviewed.

RESULTS

A total of 69 rural patients were compared with 1387 metropolitan patients. Metabolic control was comparable, with no difference in mean HbA1c (8.3%/67 mmol/mol for both groups). Treatment options varied slightly at diagnosis, while insulin pump usage was comparable between treatment settings (20.3% rural compared with 27.6% urban, P = 0.19). Of note was that the number of visits per year was higher in the rural group (3.3 per year rural compared with 2.7 urban, P < 0.001).

CONCLUSIONS

We conclude that the outreach service is able to provide a comparable level of care when the urban model is translated to a rural setting. This model may be further able to be extrapolated to other geographic areas and also other chronic health conditions of childhood.

Mutations in SLC34A3/NPT2c are associated with kidney stones and nephrocalcinosis

Compound heterozygous and homozygous (comp/hom) mutations in solute carrier family 34, member 3 (SLC34A3), the gene encoding the sodium (Na(+))-dependent phosphate cotransporter 2c (NPT2c), cause hereditary hypophosphatemic rickets with hypercalciuria (HHRH), a disorder characterized by renal phosphate wasting resulting in hypophosphatemia, correspondingly elevated 1,25(OH)2 vitamin D levels, hypercalciuria, and rickets/osteomalacia. Similar, albeit less severe, biochemical changes are observed in heterozygous (het) carriers and indistinguishable from those changes encountered in idiopathic hypercalciuria (IH). Here, we report a review of clinical and laboratory records of 133 individuals from 27 kindreds, including 5 previously unreported HHRH kindreds and two cases with IH, in which known and novel SLC34A3 mutations (c.1357delTTC [p.F453del]; c.G1369A [p.G457S]; c.367delC) were identified. Individuals with mutations affecting both SLC34A3 alleles had a significantly increased risk of kidney stone formation or medullary nephrocalcinosis, namely 46% compared with 6% observed in healthy family members carrying only the wild-type SLC34A3 allele (P=0.005) or 5.64% in the general population (P<0.001). Renal calcifications were also more frequent in het carriers (16%; P=0.003 compared with the general population) and were more likely to occur in comp/hom and het individuals with decreased serum phosphate (odds ratio [OR], 0.75, 95% confidence interval [95% CI], 0.59 to 0.96; P=0.02), decreased tubular reabsorption of phosphate (OR, 0.41; 95% CI, 0.23 to 0.72; P=0.002), and increased serum 1,25(OH)2 vitamin D (OR, 1.22; 95% CI, 1.05 to 1.41; P=0.008). Additional studies are needed to determine whether these biochemical parameters are independent of genotype and can guide therapy to prevent nephrocalcinosis, nephrolithiasis, and potentially, CKD.

Childhood insulinoma masquerading as seizure disorder

A 9 year old girl presented with seizures, weight gain and early morning behavioural changes. She had been commenced on anticonvulsants and was subsequently diagnosed with hyperinsulinaemic hypoglycaemia. This case demonstrates the importance of blood glucose monitoring in children presenting with new-onset seizures and/or with early morning or fasting behavioural changes, the challenges in localizing the lesion, as well as the difficulties in achieving normoglycaemia prior to, and immediately following, surgery.

Incidence of vitamin D deficiency rickets among Australian children: an Australian Paediatric Surveillance Unit study

OBJECTIVE

To determine the incidence of and factors associated with vitamin D deficiency rickets in Australian children.

DESIGN

18-month questionnaire-based prospective observational study, using Australian Paediatric Surveillance Unit (APSU) data.

SETTING

Australian paediatricians and child health workers, January 2006 - July 2007.

PARTICIPANTS

Children aged ≤ 15 years with vitamin D deficiency rickets (25-hydroxyvitamin D [25OHD] ≤ 50 nmol/L, and elevated alkaline phosphatase levels [> 229 IU/L] and/or radiological rickets).

MAIN OUTCOME MEASURES

Incidence of vitamin D deficiency rickets. Description of demographics, clinical presentation, identification and further analysis of overrepresented groups, and treatment regimens compared with best-practice guidelines.

RESULTS

We identified 398 children with vitamin D deficiency (55% male; median age, 6.3 years [range, 0.2-15 years]). The overall incidence in children ≤ 15 years of age in Australia was 4.9/100 000/year. All had a low 25OHD level (median, 28 nmol/L [range, 5-50 nmol]) and an elevated alkaline phosphatase level (median, 407 IU/L [range, 229-5443 IU/L]), and 48 (12%) were hypocalcaemic. Ninety-five children had wrist x-rays, of whom 67 (71%) had rachitic changes. Most (98%) had dark or intermediate skin colour and 18% of girls were partially or completely veiled. Most children were born in Africa (252; 63%) and 75% of children were refugees. Duration of exclusive breastfeeding was inversely related to serum vitamin D levels in children < 3 years of age. Empirical vitamin D treatment was given to 4% of children before diagnosis.

CONCLUSIONS

Vitamin D deficiency rickets is a significant problem in Australia among known high-risk groups. Public health campaigns to prevent, identify and tre@vitamin D deficiency, especially in high-risk groups, are essential.

Zoledronic acid improves bone mineral density, reduces bone turnover and improves skeletal architecture over 2 years of treatment in children with secondary osteoporosis

There are limited data on the use of bisphosphonate therapy for secondary osteoporoses in childhood, and no previous reports of the use of zoledronic acid in this group. We report 20 children with a variety of underlying primary diagnoses with associated secondary osteoporosis, who were treated with 3 monthly zoledronic acid for 2 years (annualised dose 0.1mg/kg/year). There was a significant improvement in lumbar spine (by 1.88 SD±1.24 over first 12 months, p<0.001) and total bone mineral density as assessed by dual energy absorptiometry (DXA) scans, with a similar increase in bone mineral content for lean tissue mass (mean increase 1.34 SD in first 12 months, p<0.001). Bone turnover was reduced with a suppression of both osteocalcin and alkaline phosphatase in the first 12 months of treatment. Skeletal architecture was improved, with increased second metacarpal cortical thickness from 2.44mm to 2.72mm (p<0.001) and improved vertebral morphometry, with 7 patients who had vertebral wedging at baseline showing improved anterior (p=0.017) and middle (p=0.001) vertebral height ratios. Aside from well reported transient side effects with the first dose, there were no adverse effects reported. No adverse effects on anthropometric parameters were seen over the course of the study. Despite all patients having sustained fragility fractures prior to treatment, no fractures were reported during the study period. Further evidence is required to confirm efficacy, with long term follow up required to assess the impact of treatment on fracture risk.

The effect of selective oestrogen receptor antagonists in an in vitro model of growth plate chondrogenesis

While oestrogen is recognized to play a key role in regulating growth, particularly in relation to epiphyseal fusion, the mechanisms that mediate its effects are still unclear. We utilized an in vitro model of chondrogenesis, the RCJ3.1C5.18 cell line, to explore the effect of oestrogen on this process. We demonstrated the presence of oestrogen receptors (ER) α and β in these cells, with increased abundance of both receptor sub-types evident as the cells differentiated. ERα localized to the nucleus, suggesting it was signalling by genomic pathways, while ERβ was seen predominantly in the cytoplasm, suggesting it may be utilizing non-genomic signalling. While exogenous oestrogen had no effect on proliferation or differentiation, we found some evidence for the endogenous production of oestrogen (intracrinology), as suggested by the expression of aromatase in these cells. Selective ERα blockade with methyl piperidinopyrazole (MPP) led to a significant reduction in both proliferation and differentiation, while ERβ blockade with R,R tetrahydrochrysene (THC) led to an increase in these parameters. This is in keeping with results from mouse knockout models suggesting that unopposed ERβ signalling leads to an inhibition of skeletal growth. Our results are further evidence for the importance of differential ER signalling in regulating chondrogenesis. Future studies examining in vivo effects of these agents are required to extrapolate these findings to a mammalian model.

Peripubertal aromatase inhibition in male rats has adverse long-term effects on bone strength and growth and induces prostatic hyperplasia

Aromatase inhibitors have been increasingly used in boys with growth retardation to prolong the duration of growth and increase final height. Multiple important roles of oestrogen in males point to potential adverse effects of this strategy. Although the deleterious effects of aromatase deficiency in early childhood and adulthood are well documented, there is limited information about the potential long-term adverse effects of peripubertal aromatase inhibition. To address this issue, we evaluated short-term and long-term effects of peripubertal aromatase inhibition in an animal model. Peripubertal male Wistar rats were treated with aromatase inhibitor letrozole or placebo and followed until adulthood. Letrozole treatment caused sustained reduction in bone strength and alteration in skeletal geometry, lowering of IGF1 levels, inhibition of growth resulting in significantly lower weight and length of treated animals and development of focal prostatic hyperplasia. Our observation of adverse long-term effects after peripubertal male rats were exposed to aromatase inhibitors highlights the need for further characterisation of long-term adverse effects of aromatase inhibitors in peripubertal boys before further widespread use is accepted. Furthermore, this suggests the need to develop more selective oestrogen inhibition strategies in order to inhibit oestrogen action on the growth plate, while beneficial effects in other tissues are preserved.

The successful use of pamidronate in an 11-year-old girl with complex regional pain syndrome: response to treatment demonstrated by serial peripheral quantitative computerised tomographic scans

Complex regional pain syndrome (CRPS) is a disorder that can cause significant functional morbidity. While it usually presents in adulthood, it has also been reported in children. Multiple treatment modalities have been reported with mixed success. Bisphosphonate therapy has been shown to be effective in adult patients, but there are limited data in children. We report the successful use of intravenous pamidronate therapy in diminishing pain, improving function, and restoring bone mass in an 11-year-old girl with CRPS of her left lower limb following a tibial fracture. Previous treatment with intense physiotherapy and regional sympathetic blockade had not improved her symptoms. Pain improved within weeks of the first pamidronate infusion, with subsequent improvement in function. The benefit in pain reduction and function was sustained during the 2-year treatment regime. Improvement in bone mass and density was demonstrated by dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computerised tomography (pQCT). pQCT scans showed marked improvement in bone size and geometry and muscle bulk on the affected side. No adverse affects were reported. We conclude that intravenous pamidronate was associated with reduced pain, a return of function, and recovery of bone and muscle parameters in a child with CRPS. Before definitive conclusions can be drawn, a randomised controlled trial similar to those undertaken in adults previously is required to fully validate this approach.

Estrogens and growth

Estrogen plays a key role in the regulation of growth in both genders, via its stimulation of the pubertal growth spurt and mediation of epiphyseal fusion. Mouse knockout models suggest a differential effect of oestrogen receptor (ER) alpha and beta on the growth plate, with ER beta possibly being more important in regulating epiphyseal fusion. Epiphyseal fusion may also depend on growth plate senescence, which is regulated by oestrogen. While molecular mechanisms for oestrogen's actions remain unclear, local production of oestrogen may be important for growth. Aromatase inhibitors appear to be effective in improving final height outcome in short stature, however long term safety data is lacking particularly in regards to reproductive function. Future studies are required to further understand the mechanisms by which ER alpha and ER beta affect growth plate function, while longer term studies of aromatase inhibitor usage, preferably utilising animal models, are required to verify the safety of these compounds.

Bisphosphonate treatment in chronic recurrent multifocal osteomyelitis

OBJECTIVE

To test the safety and efficacy of biphosphonates in chronic recurrent multifocal osteomyelitis (CRMO).

STUDY DESIGN

Five patients with CRMO, all of whom had ongoing pain and loss of function despite conventional treatment with non-steroidal anti-inflammatory agents, were treated with pamidronate (1 mg/kg/dose with a dosing frequency of 2 to 4 monthly for a total treatment duration of 12 to 42 months).

RESULTS

Pain decreased after the first infusion for 4 of 5 patients, with symptomatic improvement maintained with time. Significant improvement was seen in radiological lesions for these 4 patients.

CONCLUSION

Bisphosphonates appear to be a useful and safe adjunctive treatment in CRMO when simple therapies such as anti-inflammatory agents fail to control symptoms or cases in which lesion expansion continues.

Successful pregnancy in a patient with severe 11-beta-hydroxylase deficiency and novel mutations in CYP11B1 gene

11 beta-Hydroxylase deficiency is a rare form of congenital adrenal hyperplasia, resulting in virilization, glucocorticoid deficiency and hypertension. There have been no previous reports in the literature of a successful pregnancy in a severely affected female. We report the first successful pregnancy resulting in a live birth for a female with 11 beta-hydroxylase deficiency and outline management issues from preconception to successful birth. We also report 2 novel mutations in the CYP11B1 gene leading to 11 beta-hydroxylase deficiency.

The psychosocial impact of Klinefelter syndrome--a 10 year review

OBJECTIVE

To describe psychosocial morbidity in a cohort of young males with hypogonadism due to Klinefelter syndrome, to document the effect of androgen replacement on behaviour, to underline issues confronting clinicians involved in treatment of this condition and to demonstrate a need for a structured program for prospective intervention for this group. We also compare this group to young men with hypogonadotrophic hypogonadism.

DESIGN

A retrospective audit of patients with Klinefelter and Kallmann syndromes, presenting for medical assessment from 1994-2004.

PATIENTS

Postpubertal males with Klinefelter syndrome (n = 32) and Kallmann syndrome (n = 19) were audited by chart review for psychosocial comorbidities, pubertal management, and the need for exogenous testosterone.

RESULTS

Seventeen of 32 postpubertal patients with Klinefelter syndrome required testosterone therapy while 11 were documented to have serum testosterone in the normal adult range. All patients with Kallmann syndrome required long term testosterone treatment. Significant psychosocial and behavioural problems were present in 22/32 of patients with Klinefelter syndrome, including seven who were testosterone replete, with an identifiable pattern of disorder, including marked lack of insight, poor judgement and impaired ability to learn from adverse experience. Use of long term replacement testosterone treatment reduced episodes of behavioural indiscretion. Of those patients with Kallmann syndrome, 5/19 reported mild depressive symptoms only, all resolving with testosterone replacement.

CONCLUSION

Inadequately treated hypogonadism in Klinefelter syndrome increases recognized psychosocial morbidity. There is a need for prospectively planned and timed support for young men with Klinefelter syndrome, to ameliorate current poor psychosocial outcomes.

Spontaneous recovery of steroid-induced osteopenia

We report a case of an adolescent girl treated with high-dose oral steroids for prolonged coughing thought to be secondary to unstable asthma. Iatrogenic adrenal suppression led to clinical appearance of Cushing syndrome and associated bilateral early post-capsular cataracts, slowing of growth velocity and osteopenia. After weaning off steroids, there was a spontaneous increase in aeral lumbar bone mineral density and also catch-up growth evident over a 5-year period.

Child and adolescent growth disorders--an overview

BACKGROUND

While many children presenting with apparent disorders of growth will be short or tall children growing normally, it is important to identify those children who have an underlying pathological cause. Parental expectation and anxiety will often accompany growth issues and this needs to be addressed.

OBJECTIVE

The article aims to assist the clinician in distinguishing pathological short stature from normal variants, and to guide in the management of normal variants and common pathologies.

DISCUSSION

Pathological short stature can be distinguished from normal variants by careful history and examination followed by accurate assessment of the growth parameters of height, weight, body proportions and growth velocity, and judicious use of investigations. Growth is a dynamic process that requires multiple measurements over time. If the patient has a nonpathological cause of short stature, explanation and reassurance are critical--for both the parents and child--to feel supported and comfortable with their height outcome.

Primary adrenal insufficiency in childhood and adolescence: advances in diagnosis and management

OBJECTIVES

Primary adrenal insufficiency occurring in childhood and adolescence is due to abnormalities of gland development, gland responsiveness, and steroid biosynthesis or target organ response. Causes include autoimmune Addison's disease, tuberculosis, HIV, adrenoleukodystrophy, adrenal hypoplasia congenita and syndromes including triple A and IMAGe. We aimed to define the causes of adrenal insufficiency for a cohort of children in Melbourne.

METHODS

We reviewed the frequency and variety of presentation of primary adrenal insufficiency to the Royal Children's Hospital over the past 10 years through an audit of patient records, collating demographic information, presentation and investigations.

RESULTS

Sixteen cases (13 male, 3 female) of primary adrenal insufficiency were diagnosed at this hospital between January 1993 and July 2003. Median age at presentation was 7.7 years (range: birth to 14.8 years). Symptoms at presentation included weakness, increased pigmentation, abdominal pain, nausea, developmental delay or a reduction in school performance. Four patients presented with adrenal crisis. Median adrenocorticotrophic hormone (ACTH) at diagnosis was 246 pmol/L (range 30-969 pmol/L). Autoantibodies were positive in five patients. Five patients had elevation of very long chain fatty acids. Five patients were diagnosed with autoimmune adrenal insufficiency, five with adrenal hypoplasia congenita, five with adrenoleukodystrophy and one with IMAGe syndrome.

CONCLUSIONS

A high index of suspicion results in earlier detection and possible prevention of adrenal crisis with a reduction in associated morbidities. Definitive diagnosis is now possible for almost all cases of primary adrenal insufficiency using technologies for screening autoimmunity, adrenoleukodystrophy (ALD) and genetic screening.