Burosumab vs Phosphate/Active Vitamin D in Pediatric X-Linked Hypophosphatemia: A Subgroup Analysis by Dose Level.

CONTEXT: In an open-label, randomized, controlled, phase 3 trial in 61 children aged 1 to 12 years with X-linked hypophosphatemia (XLH), burosumab improved rickets vs continuing conventional therapy with active vitamin D and phosphate. OBJECTIVE: We conducted an analysis to determine whether skeletal responses differed when switching to burosumab vs continuing higher or lower doses of conventional therapy. METHODS: Conventional therapy dose groups were defined as higher-dose phosphate [greater than 40 mg/kg] (HPi), lower-dose phosphate [40 mg/kg or less] (LPi), higher-dose alfacalcidol [greater than 60 ng/kg] or calcitriol [greater than 30 ng/kg] (HD), and lower-dose alfacalcidol [60 ng/kg or less] or calcitriol [30 ng/kg or less] (LD). RESULTS: At week 64, the Radiographic Global Impression of Change (RGI-C) for rickets was higher (better) in children randomly assigned to burosumab vs conventional therapy for all prebaseline dose groups: HPi (+1.72 vs +0.67), LPi (+2.14 vs +1.08), HD (+1.90 vs +0.94), LD (+2.11 vs +1.06). At week 64, the RGI-C for rickets was also higher in children randomly assigned to burosumab (+2.06) vs conventional therapy for all on-study dose groups: HPi (+1.03), LPi (+1.05), HD (+1.45), LD (+0.72). Serum alkaline phosphatase (ALP) also decreased in the burosumab-treated patients more than in the conventional therapy group, regardless of on-study phosphate and active vitamin D doses. CONCLUSION: Prior phosphate or active vitamin D doses did not influence treatment response after switching to burosumab among children with XLH and active radiographic rickets. Switching from conventional therapy to burosumab improved rickets and serum ALP more than continuing either higher or lower doses of phosphate or active vitamin D.

A Novel De Novo Frameshift Pathogenic Variant in the FAM111B Resulting in Progressive Osseous Heteroplasia Phenotype.

INTRODUCTION: Progressive osseous heteroplasia (POH) is a rare, debilitating disorder characterized by heterotopic ossification in the skin and muscles, resulting in contractures of the joints and progressive loss of function. While 60-70% of the POH patients have paternally inherited, inactivating pathogenic variants in GNAS, the remaining 30-40% have no known etiology. FAM111B pathogenic variants, located on chromosome 11q12.1, cause POIKTMP (hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis), a very rare, autosomal-dominant disorder with high frequency of de novo missense pathogenic variants, which affects multiple tissues and organs, causing extensive fibrosis and muscle adiposis, though the exact mechanism is unknown. To our knowledge, there are no reports of FAM111B associated with POH. We describe the first case of POH phenotype associated with a novel de novo frameshift pathogenic variant in the FAM111B and present an analysis of the protein structure and function caused by this genomic disruption. CASE: A 15-year-old African-American male presented with generalized calcific nodules, progressive contractures, and muscle weakness leading to immobility, beginning at 6 years of age. Cutaneous examination showed generalized hard nodules varying from small to plaque-like ulcerated erupted skin lesions. Biochemical evaluation revealed 25(OH) vitamin D insufficiency (20 ng/mL), and normal levels of parathyroid hormone, FGF-23, alkaline phosphatase, calcium, and phosphorus. Skeletal survey radiographs and computed tomography (CT) of the chest, abdomen, and pelvis showed extensive soft tissue and muscle heterotopic ossifications involving shoulders, axillae, trunk, abdomen, pelvis, upper and lower extremities, in a clumped, conglomerate distribution within muscle, subcutaneous fat, and in some areas extending to the skin. There was no pulmonary fibrosis on the chest CT. The clinical and radiographic findings were most consistent with POH. A trio-clinical exome sequencing revealed a de novo heterozygous likely pathogenic variant in the FAM111B (OMIM # 615584) (c.1462delT [p.Cys488Valfs*21]). The resulted frameshift change in exon 4 replaced C-terminal region with 21 alternative amino acids. Multiple, previously reported disease-associated variants appear to localize within the trypsin-like cysteine/serine peptidase domain in which this variant occurs, supporting the functional significance of this region, though none have been previously reported to be associated with POH phenotype. Our 3D protein modeling showed obliteration of predicted protein folding and structure, and elimination of the zinc-binding domain, likely severely affecting protein function. CONCLUSION: This is the first case of POH phenotype associated with a novel de novo pathogenic frameshift variant in FAM111B. Whether the frameshift change in FAM111B predicts POH remains unclear. Further evaluations are necessary to fully elucidate this finding and the potential role and mechanism by which the FAM111B variants contributes to POH phenotype.

Efficacy of Burosumab in Adults with X-linked Hypophosphatemia (XLH): A Post Hoc Subgroup Analysis of a Randomized Double-Blind Placebo-Controlled Phase 3 Study.

The anti-fibroblast growth factor 23 monoclonal antibody burosumab corrects hypophosphatemia in adults with X-linked hypophosphatemia (XLH) and improves pain, stiffness, physical function, and fatigue. This post hoc subgroup analysis used data from the 24-week placebo-controlled period of a phase 3 study in 134 adults with XLH (ClinicalTrials.gov NCT02526160), to assess whether the benefits of burosumab are evident in 14 clinically relevant subgroups defined by baseline demographic and functional criteria, including sex, Brief Pain Inventory-short form (BPI-SF) Average And Worst Pain, region, race, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC®) Stiffness, Physical Function and Pain domains and total score, use of opioid/other pain medication, active fractures/pseudo-fractures, and 6-min walk test distance. There were no statistically significant interactions between any of the subgroups and treatment arm for any endpoint. Higher proportions of subjects achieved mean serum phosphate concentration above the lower limit of normal (the primary endpoint) with burosumab than with placebo in all subgroups. For the key secondary endpoints (WOMAC Stiffness and Physical Function; BPI-SF Worst Pain) individual subgroup categories showed improvements with burosumab relative to placebo. For additional efficacy endpoints, burosumab was favored in some subgroups but differences were not significant and confidence intervals were wide. For some endpoints the treatment effect is small at 24 weeks in all subjects. This subgroup analysis shows that burosumab was largely superior to placebo across endpoints in the 14 clinically relevant subgroup variables at 24 weeks and is likely to benefit all symptomatic adults with active XLH.

Burosumab treatment in adults with X-linked hypophosphataemia: 96-week patient-reported outcomes and ambulatory function from a randomised phase 3 trial and open-label extension.

OBJECTIVES: To report the impact of burosumab on patient-reported outcomes (PROs) and ambulatory function in adults with X-linked hypophosphataemia (XLH) through 96 weeks. METHODS: Adults diagnosed with XLH were randomised 1:1 in a double-blinded trial to receive subcutaneous burosumab 1 mg/kg or placebo every 4 weeks for 24 weeks (NCT02526160). Thereafter, all subjects received burosumab every 4 weeks until week 96. PROs were measured using the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC), Brief Pain Inventory-Short Form (BPI-SF) and Brief Fatigue Inventory (BFI), and ambulatory function was measured with the 6 min walk test (6MWT). RESULTS: Subjects (N=134) were randomised to burosumab (n=68) or placebo (n=66) for 24 weeks. At baseline, subjects experienced pain, stiffness, and impaired physical and ambulatory function. At week 24, subjects receiving burosumab achieved statistically significant improvement in some BPI-SF scores, BFI worst fatigue (average and greatest) and WOMAC stiffness. At week 48, all WOMAC and BPI-SF scores achieved statistically significant improvement, with some WOMAC and BFI scores achieving meaningful and significant change from baseline. At week 96, all WOMAC, BPI-SF and BFI achieved statistically significant improvement, with selected scores in all measures also achieving meaningful change. Improvement in 6MWT distance and percent predicted were statistically significant at all time points from 24 weeks. CONCLUSIONS: Adults with XLH have substantial burden of disease as assessed by PROs and 6MWT. Burosumab treatment improved phosphate homoeostasis and was associated with a steady and consistent improvement in PROs and ambulatory function. TRIAL REGISTRATION NUMBER: NCT02526160.

Economic burden of growth hormone deficiency in a US pediatric population.

BACKGROUND: Pediatric growth hormone deficiency (GHD) is a rare disorder of short stature that is currently treated with daily injections of somatropin. In addition to short stature, GHD is associated with other comorbidities such as impaired musculoskeletal development, cardiovascular disease, and decreased quality of life. OBJECTIVE: To analyze somatropin utilization, adherence, and health care costs among children with GHD who had either Medicaid or commercial health insurance. METHODS: Children (aged < 18 years) with a GHD diagnosis between January 1, 2008, and December 31, 2017, were identified in the IBM MarketScan Commercial and Medicaid databases. Patients with at least 12- and 6-month continuous enrollment pre- and postdiagnosis were eligible. Children with GHD were direct matched (1:3) to controls without GHD (or other short stature-related disorders) on age, gender, plan type, region, and race (Medicaid only). Index date was the date of the first GHD diagnosis during the selection window for GHD patients and using random assignment for controls. Patients were followed until the end of continuous database enrollment or December 31, 2018. Baseline comorbidities and medications were measured during the 12 months pre-index, whereas somatropin treatment patterns along with all-cause and GHD-related health care costs were measured during the variable follow-up period. Multivariable modeling was used to compare costs between GHD patients and controls and between somatropin-treated and -untreated GHD patients while adjusting for baseline characteristics. RESULTS: There were 6,820 Medicaid and 14,070 commercial patients with GHD who met the study inclusion criteria. Mean (SD) age at index was 9.5 (4.5) years for Medicaid patients and 11.1 (3.7) years for commercial patients. The majority of patients were male (> 65%), and mean follow-up time for all cases and controls was 3-4 years. Overall, 63.2% of Medicaid and 68.4% of commercial GHD patients were treated with somatropin at some point during follow-up. Among Medicaid GHD patients, the treatment rate was highest among White males and lowest among Black females. Adherence was low as the proportion of days covered was ≥ 80% for only 18.4% of Medicaid patients and 32.3% of commercial patients and 49.1% of treated Medicaid and 24.3% of treated commercial patients discontinued before turning age 13. After adjusting for baseline characteristics, all-cause non-somatropin annualized costs were 5.67 times higher (Δ$19,309) for Medicaid GHD patients and 5.46 times higher (Δ$12,305) for commercial GHD patients than matched non-GHD controls. Adjusted all-cause non-somatropin annualized costs were 0.59 times lower (Δ$14,416) for treated Medicaid patients and 0.69 times lower (Δ$7,650) for treated commercial patients than for untreated patients. CONCLUSIONS: Pediatric GHD presents a significant health care burden, and many patients remain untreated or undertreated. Untreated GHD was associated with higher non-somatropin health care costs than treated GHD. Strategies to optimize treatment and improve adherence may reduce the health care burden faced by these patients. DISCLOSURES: This study was funded by Ascendis Pharma, Inc. Smith and Pitukcheewanont are employed by Ascendis Pharma, Inc. Manjelievskaia, Lopez-Gonzalez, and Morrow are employed by IBM Watson Health, which received funding from Ascendis Pharma, Inc., to conduct this study. Kaplowitz is a paid consultant of Ascendis Pharma, Inc.

Patient-Reported Outcomes from a Randomized, Active-Controlled, Open-Label, Phase 3 Trial of Burosumab Versus Conventional Therapy in Children with X-Linked Hypophosphatemia.

Changing to burosumab, a monoclonal antibody targeting fibroblast growth factor 23, significantly improved phosphorus homeostasis, rickets, lower-extremity deformities, mobility, and growth versus continuing oral phosphate and active vitamin D (conventional therapy) in a randomized, open-label, phase 3 trial involving children aged 1-12 years with X-linked hypophosphatemia. Patients were randomized (1:1) to subcutaneous burosumab or to continue conventional therapy. We present patient-reported outcomes (PROs) from this trial for children aged ≥ 5 years at screening (n = 35), using a Patient-Reported Outcomes Measurement Information System (PROMIS) questionnaire and SF-10 Health Survey for Children. PROMIS pain interference, physical function mobility, and fatigue scores improved from baseline with burosumab at weeks 40 and 64, but changed little with continued conventional therapy. Pain interference scores differed significantly between groups at week 40 (- 5.02, 95% CI - 9.29 to - 0.75; p = 0.0212) but not at week 64. Between-group differences were not significant at either week for physical function mobility or fatigue. Reductions in PROMIS pain interference and fatigue scores from baseline were clinically meaningful with burosumab at weeks 40 and 64 but not with conventional therapy. SF-10 physical health scores (PHS-10) improved significantly with burosumab at week 40 (least-squares mean [standard error] + 5.98 [1.79]; p = 0.0008) and week 64 (+ 5.93 [1.88]; p = 0.0016) but not with conventional therapy (between-treatment differences were nonsignificant). In conclusion, changing to burosumab improved PRO measures, with statistically significant differences in PROMIS pain interference at week 40 versus continuing with conventional therapy and in PHS-10 at weeks 40 and 64 versus baseline.Trial registration: ClinicalTrials.gov NCT02915705.

Null mutations of NEUROG3 are associated with delayed-onset diabetes mellitus.

Biallelic mutations of the gene encoding the transcription factor NEUROG3 are associated with a rare disorder that presents in neonates as generalized malabsorption - due to a complete absence of enteroendocrine cells - followed, in early childhood or beyond, by insulin-dependent diabetes mellitus (IDDM). The commonly delayed onset of IDDM suggests a differential requirement for NEUROG3 in endocrine cell generation in the human pancreas versus the intestine. However, previously identified human mutations were hypomorphic and, hence, may have had residual function in pancreas. We report 2 patients with biallelic functionally null variants of the NEUROG3 gene who nonetheless did not present with IDDM during infancy but instead developed permanent IDDM during middle childhood ages. The variants showed no evidence of function in traditional promoter-based assays of NEUROG3 function and also failed to exhibit function in a variety of potentially novel in vitro and in vivo molecular assays designed to discern residual NEUROG3 function. These findings imply that, unlike in mice, pancreatic endocrine cell generation in humans is not entirely dependent on NEUROG3 expression and, hence, suggest the presence of unidentified redundant in vivo pathways in human pancreas capable of yielding ß cell mass sufficient to maintain euglycemia until early childhood.

Quantifying RANKL and OPG levels in healthy children: A large cross-sectional analysis.

BACKGROUND: There have been new advances in understanding bone remodeling on a molecular level including the RANKL-OPG pathway, leading to advancements in targeted therapeutic intervention. There is however limited data in pediatrics with little known on normative values in healthy children. This is the largest cohort to quantify RANKL, OPG, and RANKL: OPG levels in healthy children as well as study the influence of age, gender, Tanner stage, and BMI in this population. METHODS: Healthy subjects, 1-21 years of age, were recruited from general pediatric clinics affiliated with CHLA and in collaboration with samples stored from a previously completed study. Healthy children were defined as those with no chronic disease, daily medication, or fractures in the past six months. Free soluble RANKL and OPG levels were quantified using a sandwich ELISA. RESULTS: Three hundred samples were collected with overall serum concentrations of RANKL, OPG and RANKL: OPG of 0.28 pmol/L, 3.56 pmol/L and 0.08 pmol/L, respectively. Serum RANKL and RANKL: OPG concentrations were significantly different by age (p = 0.0001 and 0.0027, respectively). There was an overall downward trend by age except in the 11-15-year age group where a slight increase was noted. RANKL concentrations were also significantly different between Tanner stages, with highest concentrations seen at Tanner 3 (p = 0.0481), and zBMI (p = 0.001). OPG was inversely correlated with zBMI, but not influenced by gender, age, or Tanner stage. CONCLUSION: We showed significant difference in RANKL levels by age, Tanner stage, and zBMI. OPG was inversely correlated with zBMI. Insight into circulating levels of RANKL, OPG and RANKL: OPG in healthy children may be a potential tool to better understand disease states in pediatrics. Future studies are needed to evaluate the clinical significance of RANKL and OPG levels for diagnostic and therapeutic purposes in this population.

Continued Beneficial Effects of Burosumab in Adults with X-Linked Hypophosphatemia: Results from a 24-Week Treatment Continuation Period After a 24-Week Double-Blind Placebo-Controlled Period.

Burosumab, a fully human monoclonal antibody to FGF23, is the only approved treatment for X-linked hypophosphatemia (XLH), a rare genetic disorder characterized by renal phosphate wasting and substantial cumulative musculoskeletal morbidity. During an initial 24-week randomized, controlled trial, 134 adults with XLH received burosumab 1 mg/kg (n = 68) or placebo (n = 66) every 4 weeks. After 24 weeks, all subjects received open-label burosumab until week 48. This report describes the efficacy and safety of burosumab during the open-label treatment period. From weeks 24-48, serum phosphorus concentrations remained normal in 83.8% of participants who received burosumab throughout and were normalized in 89.4% who received burosumab after placebo. By week 48, 63.1% of baseline fractures/pseudofractures healed fully with burosumab, compared with 35.2% with burosumab after placebo. In both groups, burosumab was associated with clinically significant and sustained improvement from baseline to week 48 in scores for patient-reported outcomes of stiffness, pain, physical function, and total distance walked in 6 min. Rates of adverse events were similar for burosumab and placebo. There were no fatal adverse events or treatment-related serious adverse events. Nephrocalcinosis scores did not change from baseline by more than one grade at either week 24 or 48. These data demonstrate that in participants with XLH, continued treatment with burosumab is well tolerated and leads to sustained correction of serum phosphorus levels, continued healing of fractures and pseudofractures, and sustained improvement in key musculoskeletal impairments.

Burosumab versus conventional therapy in children with X-linked hypophosphataemia: a randomised, active-controlled, open-label, phase 3 trial.

BACKGROUND: X-linked hypophosphataemia in children is characterised by elevated serum concentrations of fibroblast growth factor 23 (FGF23), hypophosphataemia, rickets, lower extremity bowing, and growth impairment. We compared the efficacy and safety of continuing conventional therapy, consisting of oral phosphate and active vitamin D, versus switching to burosumab, a fully human monoclonal antibody against FGF23, in paediatric X-linked hypophosphataemia. METHODS: In this randomised, active-controlled, open-label, phase 3 trial at 16 clinical sites, we enrolled children with X-linked hypophosphataemia aged 1-12 years. Key eligibility criteria were a total Thacher rickets severity score of at least 2·0, fasting serum phosphorus lower than 0·97 mmol/L (3·0 mg/dL), confirmed PHEX (phosphate-regulating endopeptidase homolog, X-linked) mutation or variant of unknown significance in the patient or a family member with appropriate X-linked dominant inheritance, and receipt of conventional therapy for at least 6 consecutive months for children younger than 3 years or at least 12 consecutive months for children older than 3 years. Eligible patients were randomly assigned (1:1) to receive either subcutaneous burosumab starting at 0·8 mg/kg every 2 weeks (burosumab group) or conventional therapy prescribed by investigators (conventional therapy group). Both interventions lasted 64 weeks. The primary endpoint was change in rickets severity at week 40, assessed by the Radiographic Global Impression of Change global score. All patients who received at least one dose of treatment were included in the primary and safety analyses. The trial is registered with ClinicalTrials.gov, number NCT02915705. FINDINGS: Recruitment took place between Aug 3, 2016, and May 8, 2017. Of 122 patients assessed, 61 were enrolled. Of these, 32 (18 girls, 14 boys) were randomly assigned to continue receiving conventional therapy and 29 (16 girls, 13 boys) to receive burosumab. For the primary endpoint at week 40, patients in the burosumab group had significantly greater improvement in Radiographic Global Impression of Change global score than did patients in the conventional therapy group (least squares mean +1·9 [SE 0·1] with burosumab vs +0·8 [0·1] with conventional therapy; difference 1·1, 95% CI 0·8-1·5; p<0·0001). Treatment-emergent adverse events considered possibly, probably, or definitely related to treatment by the investigator occurred more frequently with burosumab (17 [59%] of 29 patients in the burosumab group vs seven [22%] of 32 patients in the conventional therapy group). Three serious adverse events occurred in each group, all considered unrelated to treatment and resolved. INTERPRETATION: Significantly greater clinical improvements were shown in rickets severity, growth, and biochemistries among children with X-linked hypophosphataemia treated with burosumab compared with those continuing conventional therapy. FUNDING: Ultragenyx Pharmaceutical and Kyowa Kirin International.

A case of severe TBCE-negative hypoparathyroidism-retardation-dysmorphism syndrome: Case report and literature review.

Hypoparathyroidism-retardation-dysmorphism syndrome (HRD) is a rare autosomal recessive disorder attributed to the mutations in the tubulin-specific chaperone E (TBCE) gene, which is vital for microtubule function during mitosis, organelle positioning, and neuronal cytokinesis. HRD is a congenital syndromic hypoparathyroidism associated with growth deficiency, microcephaly, intellectual disability, ocular anomalies, and facial dysmorphism. To our knowledge, there is only one published case of mild HRD-like syndrome with no identifiable genetic etiology. We report a case of severe TBCE-negative phenotypic HRD in a 4-year-old female from India presenting with hypocalcemic seizures due to congenital hypoparathyroidism, extreme microcephaly, growth deficiency, ocular anomalies, and facial dysmorphism. SNP microarray and whole exome sequencing (WES) did not detect any abnormalities in TBCE or other genes of interest. WES revealed two variants of unknown clinical significance in CASC5 gene, which codes for a protein in the kinetochore and, interestingly similar to TBCE, is essential for proper microtubule function during mitosis and cell proliferation and has been implicated in primary microcephaly disorders. However, further targeted sequencing in the parents revealed both variants inherited from the unaffected mother. Significant copy number variant noise in the proband and her parents limited further analysis. At this time the role of variants in the CASC5 gene is unclear and cannot explain our patient's phenotype. In conclusion, we report a severe case of phenotypic HRD syndrome, in which extensive genetic evaluation failed to reveal an etiology. Our case demonstrates that the pathogenesis of HRD may be genetically heterogenous, meriting further genetic investigations.

A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Trial Evaluating the Efficacy of Burosumab, an Anti-FGF23 Antibody, in Adults With X-Linked Hypophosphatemia: Week 24 Primary Analysis.

In X-linked hypophosphatemia (XLH), inherited loss-of-function mutations in the PHEX gene cause excess circulating levels of fibroblast growth factor 23 (FGF23), leading to lifelong renal phosphate wasting and hypophosphatemia. Adults with XLH present with chronic musculoskeletal pain and stiffness, short stature, lower limb deformities, fractures, and pseudofractures due to osteomalacia, accelerated osteoarthritis, dental abscesses, and enthesopathy. Burosumab, a fully human monoclonal antibody, binds and inhibits FGF23 to correct hypophosphatemia. This report summarizes results from a double-blind, placebo-controlled, phase 3 trial of burosumab in symptomatic adults with XLH. Participants with hypophosphatemia and pain were assigned 1:1 to burosumab 1 mg/kg (n = 68) or placebo (n = 66) subcutaneously every 4 weeks (Q4W) and were comparable at baseline. Across midpoints of dosing intervals, 94.1% of burosumab-treated participants attained mean serum phosphate concentration above the lower limit of normal compared with 7.6% of those receiving placebo (p < 0.001). Burosumab significantly reduced the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC) stiffness subscale compared with placebo (least squares [LS] mean ± standard error [SE] difference, -8.1 ± 3.24; p = 0.012). Reductions in WOMAC physical function subscale (-4.9 ± 2.48; p = 0.048) and Brief Pain Inventory worst pain (-0.5 ± 0.28; p = 0.092) did not achieve statistical significance after Hochberg multiplicity adjustment. At week 24, 43.1% (burosumab) and 7.7% (placebo) of baseline active fractures were fully healed; the odds of healed fracture in the burosumab group was 16.8-fold greater than that in the placebo group (p < 0.001). Biochemical markers of bone formation and resorption increased significantly from baseline with burosumab treatment compared with placebo. The safety profile of burosumab was similar to placebo. There were no treatment-related serious adverse events or meaningful changes from baseline in serum or urine calcium, intact parathyroid hormone, or nephrocalcinosis. These data support the conclusion that burosumab is a novel therapeutic addressing an important medical need in adults with XLH.© 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

X-linked Hypophosphatemic Rickets, del(2)(q37.1;q37.3) Deletion Syndrome and Mosaic Turner Syndrome, mos 45,X/46,X, del(2)(q37.1;q37.3) in a 3-year-old Female.

There are currently no published cases that report concomitant Turner syndrome (TS), 2q37 deletion syndrome and X-linked hypophosphatemic rickets (XLH). Interestingly, since the clinical phenotypes of TS and 2q37 deletion syndrome overlap, the correct diagnosis may be missed without a standardized approach to genetic testing consisting of both karyotype and microarray. Both chromosome anomalies have been associated with short stature and a variety of skeletal abnormalities however to date no reports have associated these syndromes in association with a phosphate regulating endopeptidase homolog, X-linked (PHEX) gene deletion resulting in XLH. We report a 3-year-old female with 3 concurrent genetic disorders including a 9.98 Mb terminal deletion of chromosome 2: del(2)(q37.1;q37.3), XLH secondary to a small microdeletion of part of the PHEX gene, and mosaic TS (mos 45,X[32]/46,X[18]). This is the first case report of a patient with 2q37 deletion syndrome and mosaic TS (mos 45,X[32]/46,X[18]) found to have XLH secondary to an interstitial constitutional PHEX gene deletion. Her severe phenotype and multiple genotypic findings reinforce the importance of thorough genetic testing in the setting of complicated phenotypic presentations.

A novel SLC12A1 gene mutation associated with hyperparathyroidism, hypercalcemia, nephrogenic diabetes insipidus, and nephrocalcinosis in four patients.

Solute Carrier Family 12 member 1 (SLC12A1) gene encodes the sodium-potassium-chloride co-transporter (NKCC2) at the apical membrane of the thick ascending loop of Henle (TAL). Bartter's syndrome (BS) type I is a rare, autosomal recessive, renal tubular disorder associated with mutation of the SLC12A1 gene. Presenting features include: hypokalemic metabolic alkalosis, hypercalciuria and nephrocalcinosis. The many allelic variants reported present with a spectrum of phenotypes, biochemical abnormalities and clinical severities. However, to date, only two reports have described hyperparathyroidism and hypercalcemia in patients with SLC12A1 gene mutations. We describe 4 patients with 4 novel mutation variants in the SLC12A1 gene (c.735C>G, c.1137del, c.2498-2499del, and c.1833delT) presenting with variable degrees of hyperparathyroidism, hypercalcemia, hypokalemic metabolic alkalosis, nephrocalcinosis, and nephrogenic diabetes insipidus. The link between calcium and parathyroid hormone abnormalities in patients with SLC12A1 mutations is unclear; the cases described suggest an association between primary hyperparathyroidism and loss of function mutation of SLC12A1, which may result in an aberrant threshold of the calcium sensing receptor at the level of the kidney.

Generalized Arterial Calcification in a Recipient Twin: Discordant Fetal Hemodynamics Result in Differing Phenotypes in Monozygotic Twins with an ABCC6 Mutation.

Recipients of the twin-twin transfusion syndrome (TTTS) often develop cardiac manifestations, but arterial calcification has rarely been reported. Generalized arterial calcification of infancy (GACI) is a genetic disorder with high infantile mortality. We report the case of a TTTS recipient with moderate cardiomyopathy at diagnosis who developed progressive calcification of the pulmonary arteries and aorta after successful in utero laser therapy. Postnatally, both twins were diagnosed with a heterozygous ABCC6 gene mutation associated with GACI. The recipient had progressive supravalvular pulmonary and aortic stenosis, was treated with bisphosphonate therapy, and successfully underwent cardiac surgery at 4 months of age. The donor twin with the same mutation remained phenotypically normal at 15 months of age. This case illustrates monozygotic fetuses with discordant in utero hemodynamics, with subsequent development of phenotypic differences. TTTS recipients with arterial calcifications should undergo genetic testing for GACI.

A germline mutation of HRPT2/CDC73 (70 G>T) in an adolescent female with parathyroid carcinoma: first case report and a review of the literature.

Parathyroid carcinoma is a rare cause of primary hyperparathyroidism amongst children, with only nine previously reported cases. The objective of the study was to present the first pediatric case with a germline CDC73 (formerly known as HRPT2) mutation, and to review the literature. A 14-year-old girl presented with pathologic slipped capital femoral epiphysis (SCFE). The patient was noted to have an elevated calcium level of 3.4 mmol/L (13.4 mg/dL), a parathyroid hormone (PTH) level of 1013 ng/L (1013 pg/mL), and a 3-cm palpable neck mass. Ultrasound and 99mTc-Sestamibi confirmed the suspicion of a parathyroid mass. Intraoperative findings and pathology confirmed the diagnosis of parathyroid carcinoma. Post-operative PTH decreased to 14 ng/L (14 pg/mL). Genetic testing showed a germline 70 G>T HRPT2/CDC73 mutation. This is the first case documenting a germline 70 G>T HRPT2/CDC73 gene mutation in a pediatric parathyroid carcinoma. Patients with sporadic parathyroid carcinoma may benefit from HRPT2/CDC73 gene mutation screening.

Effects of vitamin D repletion on glycemic control and inflammatory cytokines in adolescents with type 1 diabetes.

OBJECTIVE: Little is known about the relationship between vitamin D deficiency and adolescents with type 1 diabetes. On the basis of adult studies showing that vitamin D improves insulin sensitivity and decreases inflammatory cytokines linked to microvascular complications, we hypothesized that treating vitamin D deficiency in adolescents with type 1 diabetes would improve glycemia and reduce inflammatory markers. RESEARCH DESIGN AND METHODS: This was a randomized, prospective, crossover study of 25 adolescents with type 1 diabetes for at least a year (aged: 13-21 yr; 62% female; 62% Hispanic) and vitamin D deficiency (25-OH vitamin D ≤30 ng/mL). Subjects received vitamin D3 (20 000 IU/week) for 6 months, either immediately or after 6 months of observation. RESULTS: At baseline, 63% of subjects screened were vitamin D deficient and randomized. Interleukin-6 (IL-6) was significantly higher in the vitamin D deficient group compared with the sufficient group (medians: 0.36 vs. 0.18) (p = 0.026), whereas neither C-reactive protein (CRP) nor tumor necrosis factor-α (TNF-α) differed. Vitamin D treatment increased serum levels of 25-OH vitamin D from 22 ± 5.3 to 34.3 ± 12.1 ng/mL (p < 0.01). However, treatment did not affect glycated hemoglobin (HbA1c), insulin dosage, CRP, interleukin-6 (IL-6), or TNF-α. CONCLUSIONS: Vitamin D deficiency is prevalent in the adolescent type 1 diabetes population, and could be associated with changes in inflammatory markers. However, vitamin D repletion over 6 months did not affect glycemia or markers of inflammation in our study, highlighting the need for additional research to validate these findings.

Progressive osseous heteroplasia, as an isolated entity or overlapping with Albright hereditary osteodystrophy.

INTRODUCTION: Progressive osseous heteroplasia (POH) is a condition of invasive heterotopic ossification. Reports of patients with mild POH with Albright hereditary osteodystrophy (AHO), specifically pseudohypoparathyroidism type Ia (PHP Ia) with hormonal resistance, suggest the possibility of a common molecular basis. GNAS has been implicated to account for overlapping features of POH and PHP Ia. Case 1: A 4-year-old boy with obesity, speech delay, and expanding subcutaneous masses on buttock/forearm. Physical exam revealed round facies and brachydactyly. Blood tests showed normal Ca, P, Mg, 25-OH vitamin D levels but elevated parathyroid hormone (PTH) and thyroid-stimulating hormone (TSH). Abdominal computed tomography (CT) showed areas with calcifications in the subcutaneous tissue, fat, and muscle. Pathology of excised tissue revealed ossifications. Genomic study revealed no GNAS mutation. He had POH and PHP Ia. Case 2: A 3-year-old boy with painful ossifications in the left lower extremity. Lab tests were notable for elevated PTH and high-normal TSH. The CT-scan showed subcutaneous/intramuscular calcifications. Genetic testing showed GNAS mutation in exon 12 [c.1024C>T (R342X)]. Patient had POH and PHP Ia. Case 3: A 9-year-old boy with knee pain and subcutaneous ossifications in back and upper/lower extremity, causing significantly limited joint mobility. Lab tests were normal. The CT-scan showed areas corresponding to subcutaneous/intramuscular ossifications throughout torso and extremities, consistent with POH. There was no GNAS mutation. CONCLUSIONS: Patients with heterotopic ossifications present with a wide spectrum of disease. Although GNAS-based mutations have been postulated to account for overlapping features of AHO and POH, normal DNA studies in certain patients with POH/AHO suggest that there may exist other molecular/epigenetic mechanisms explaining their overlapping features.

Bone health in children and adolescents: risk factors for low bone density.

Osteoporosis is a common disease that is characterized by low bone mineral density (BMD). Decreased BMD is associated with increased fracture risk. In adults, normal BMD results from the balance between accrual of peak bone mass (PBM) at the end of adolescence, and subsequent bone loss with age. Although environmental factors play a role, hereditary factors are the major contributors (up to 80%) to the variability in PBM. This review examines the effects of genetics, physical activity and immobilization, smoking, chronic diseases and medications, vitamin D, calcium, and various other dietary factors on bone integrity in children, adolescents, and adults.

Identifying an Ectopic Parathyroid Adenoma Using 4DCT in a Pediatric Patient with Persistent Primary Hyperparathyroidism.

We present a case of an ectopic mediastinal parathyroid adenoma detected with 4-dimensional computed tomography (4DCT) in a patient with persistent primary hyperparathyroidism and failed neck exploration. We discuss the utility of 4DCT in the localization of these lesions and offer an algorithm that implements the use of 4DCT early on when standard imaging techniques are nonlocalizing.