O108 Central adiposity influences serum calcium concentrations and increases risk of kidney stone disease

Introduction

Serum calcium (SCa) and adiposity are associated with kidney stone disease (KSD). We used conventional and genetic epidemiological approaches to further understanding of these relationships.

Methods

Waist-hip ratio (WHR), a marker of central adiposity, SCa and KSD data were analysed by adjusted linear regression using UK Biobank participants. Univariable, multivariable and mediation Mendelian randomisation (MR) were undertaken using 316 and 246 genetic instruments for WHR and SCa, respectively.

Results

Observational analyses of 3,466 KSD cases and 489,944 controls showed that participants of normal BMI (20–25kg/m2) but in the fifth quintile for WHR have greater risk of incident KSD compared to the first quintile (HR=1.39 (95%CI=1.18–1.63)). After adjustment for sex, age, serum vitamin D, and phosphate, higher WHR was positively associated with SCa (ß=0.04, 95%=CI 0.04–0.05, P<0.001). Univariable MR demonstrated that relative risk of KSD increases with increasing WHR and SCa; 1 standard deviation (SD) increases relative risk by 46% (95%CI=1.27–1.67, P=5.9e-8) and 63% (95%CI=1.37–1.93, P=2.0E-8), respectively. A 1 SD increase in WHR increases SCa by 0.11mmol/L (95%CI=0.07–0.14, P=1.8e-8). Multivariable MR revealed that SCa and WHR independently increase KSD relative risk (OR=1.71, 95%CI=1.49–1.96, P<0.001 and OR=1.41, 95%CI=1.17–1.69, P<0.001 respectively). Mediation MR established that 14% of the effect of WHR on KSD risk is mediated via alterations in SCa.

Conclusion

Central adiposity is causally linked to KSD, partly by raising SCa. Mechanisms by which central adiposity increases KSD risk, independent of and via SCa, remain to be revealed and may identify novel therapeutic methods for KSD.

Take-home message

Central adiposity and serum calcium are independent, causal risk factors for kidney stone disease. One mechanism by which central obesity increases risk of kidney stone disease is by influencing serum calcium concentrations.

Age-dependent changes in protein incorporation into collagen-rich tissues of mice by in vivo pulsed SILAC labelling

Collagen-rich tissues have poor reparative capacity that predisposes to common age-related disorders such as osteoporosis and osteoarthritis. We used in vivo pulsed SILAC labelling to quantify new protein incorporation into cartilage, bone, and skin of mice across the healthy life course. We report dynamic turnover of the matrisome, the proteins of the extracellular matrix, in bone and cartilage during skeletal maturation, which was markedly reduced after skeletal maturity. Comparing young adult with older adult mice, new protein incorporation was reduced in all tissues. STRING clustering revealed changes in epigenetic modulators across all tissues, a decline in chondroprotective growth factors such as FGF2 and TGFβ in cartilage, and clusters indicating mitochondrial dysregulation and reduced collagen synthesis in bone. Several pathways were implicated in age-related disease. Fewer changes were observed for skin. This methodology provides dynamic protein data at a tissue level, uncovering age-related molecular changes that may predispose to disease.

Medial Arterial Calcification: JACC State-of-the-Art Review

Medial arterial calcification (MAC) is a chronic systemic vascular disorder distinct from atherosclerosis that is frequently but not always associated with diabetes mellitus, chronic kidney disease, and aging. MAC is also a part of more complex phenotypes in numerous less common diseases. The hallmarks of MAC include disseminated and progressive precipitation of calcium phosphate within the medial layer, a prolonged and clinically silent course, and compromise of hemodynamics associated with chronic limb-threatening ischemia. MAC increases the risk of complications during vascular interventions and mitigates their outcomes. With the exception of rare monogenetic defects affecting adenosine triphosphate metabolism, MAC pathogenesis remains unknown, and causal therapy is not available. Implementation of genetics and omics-based approaches in research recognizing the critical importance of calcium phosphate thermodynamics holds promise to unravel MAC molecular pathogenesis and to provide guidance for therapy. The current state of knowledge concerning MAC is reviewed, and future perspectives are outlined.

MANAGEMENT OF ENDOCRINE DISEASE: Unmet therapeutic, educational and scientific needs in parathyroid disorders

PARAT, a new European Society of Endocrinology program, aims to identify unmet scientific and educational needs of parathyroid disorders, such as primary hyperparathyroidism (PHPT), including parathyroid cancer (PC), and hypoparathyroidism (HypoPT). The discussions and consensus statements from the first PARAT workshop (September 2018) are reviewed. PHPT has a high prevalence in Western communities, PHPT has a high prevalence in Western communities, yet evidence is sparse concerning the natural history and whether morbidity and long-term outcomes are related to hypercalcemia or plasma PTH concentrations, or both. Cardiovascular mortality and prevalence of low energy fractures are increased, whereas Quality of Life is decreased, although their reversibility by treatment of PHPT has not been convincingly demonstrated. PC is a rare cause of PHPT, with an increasing incidence, and international collaborative studies are required to advance knowledge of the genetic mechanisms, biomarkers for disease activity, and optimal treatments. For example, ~20% of PCs demonstrate high mutational burden, and identifying targetable DNA variations, gene amplifications and gene fusions may facilitate personalized care, such as different forms of immunotherapy or targeted therapy. HypoPT, a designated orphan disease, is associated with a high risk of symptoms and complications. Most cases are secondary to neck surgery. However, there is a need to better understand the relation between disease biomarkers and intellectual function, and to establish the role of PTH in target tissues, as these may facilitate the appropriate use of PTH substitution therapy. Management of parathyroid disorders is challenging, and PARAT has highlighted the need for international transdisciplinary scientific and educational studies in advancing in this field.

MON-335 Phenocopy of Multiple Endocrine Neoplasia Type 1 (MEN1) Due to a Germline Cell Division Cycle 73 (CDC73) Variant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined occurrence of parathyroid tumors, and neuroendocrine tumors (NETs) of the pituitary and pancreas. MEN1 is caused by germline mutations of the tumor suppressor gene MEN1, which are found in >75% of MEN1 patients. The remaining patients may have mutations involving: as yet unidentified genes; or other genes with known involvement in endocrine tumors, e.g. cyclin dependent kinase inhibitor 1B (CDKN1B) which is associated with MEN4. Here, we report a patient who had primary hyperparathyroidism, acromegaly, and a pancreatic NET that showed immuno-staining for glucagon and chromogranin A, which are consistent with MEN1. However, mutational analysis did not identify a MEN1 mutation, and analysis of other genes was undertaken, after informed consent was obtained from the patient. These genes include: CDKN1B; CDKN1A; CDKN2B; CDKN2C;cell cycle division 73 (CDC73), causative for hyperparathyroidism-jaw tumour (HPT-JT) syndrome, an autosomal dominant disorder characterised by occurrence of parathyroid tumors, ossifying fibromas of the jaw, renal tumours and uterine tumors; calcium sensing receptor (CASR), causative for familial hypocalciuric hypercalcemia type 1 (FHH1); and aryl-hydrocarbon receptor-interacting protein (AIP), causative for familial pituitary tumors. This revealed a heterozygous c.1138C>T (p.Leu380Phe) missense mutation of CDC73. This is likely a disease-causing mutation as: 1) the p.Leu380Phe substitution is not present in >120,000 alleles of The Exome Aggregation Consortium (ExAc) database; 2) involves an evolutionary conserved Leu380 residue; and 3) is situated within the parafibromin domain predicted to interact with the polymerase associated factor 1 (PAF1) and RNA polymerase II, (POLR2A) complex. In addition, RNA-Scope analysis, to detect specific CDC73 mRNA transcripts in paraffin embedded sections, of the patient’s pancreatic NET revealed that CDC73 mRNA expression was significantly decreased by >13% (p<0.005) in the tumor cells, compared to normal adjacent islets. Thus, our results suggest the spectrum of tumours associated with CDC73 mutations also includes pancreatic NETs, and demonstrate that CDC73 mutations may result in a phenocopy of MEN1.

MON-468 Selective Inhibition of Epigenetic Pathways Has Anti-Proliferative and Pro-Apoptotic Effects on the Mouse Corticotroph Tumor Cells, AtT20

Corticotrophinomas, which are neuroendocrine tumors (NETs) and represent >10% of all surgically removed pituitary adenomas, cause Cushing’s disease that is associated with hypersecretion of adrenocorticotropic hormone (ACTH) leading to excessive production of glucocorticoids by the adrenal cortex. Trans-sphenoidal hypophysectomy is the treatment of choice for corticotrophinomas, with medical treatments being reserved for patients who have contraindications for surgery. However, these treatments are often ineffective. Improved therapeutic approaches are required, and we have therefore assessed the efficacy of epigenetic modulators, a new class of anti-cancer drugs that have been reported to be effective in treating pancreatic NETs. Specifically, we assessed the anti-proliferative and pro-apoptotic effects of the bromo and extra terminal domain (BET) inhibitors JQ1 and PFI-1, in the mouse corticotrophinoma cell line AtT20, using Cell Titer Blue and Caspase Glo assays, respectively. JQ1, after 96h treatment, was more efficacious than PFI-1. Thus, JQ1 significantly decreased proliferation by 95%, (p<0.0005), and significantly increased apoptosis >50-fold (p<0.0005), compared to control treated cells; whereas PFI-1 decreased proliferation by 43% (p<0.0005), but did not significantly alter apoptosis. Furthermore, AtT20 cells did not resume proliferating for up to 96 hours after the removal of JQ1 from the media. In addition, RNA-sequence (RNA-Seq) analysis revealed that JQ1 treatment significantly altered the expression of genes involved in apoptosis, including Nuclear Factor Kappa B Subunit 1 (Nfκb1) and Baculoviral IAP Repeat Containing 3 (Birc3), as well as genes associated with the somatostatin receptor type 2 (SSTR2) anti-proliferative signaling pathway, including Sstr2. The down regulation of these genes was confirmed using quantitative PCR, which showed decreases in Nfkb1, Birc3 and Sstr2 mRNA of 2.9-fold (p<0.0009), 1.7-fold (p<0.005), and 1.5-fold (p<0.005), respectively. In addition, Western blot analysis showed decreases in Nfkb1, cIAP2 and SSTR2 protein expression of 1.5-fold (p<0.05), 1.9-fold (p<0.05), and 2.3-fold (p<0.05), respectively. Thus our results, which demonstrate that JQ1 treatment is both anti-proliferative and pro-apoptotic in ACTH-secreting cells, reveal that BET inhibition may provide a novel approach for the treatment of corticotrophinomas.

MON-539 Mice Harboring a Germline Heterozygous AP2S1 Mutation, Arg15Leu, Are a Model for Familial Hypocalciuric Hypercalcemia Type 3 (FHH3)

Familial hypocalciuric hypercalcemia (FHH) is a disorder of calcium homeostasis comprising three reported genetic variants: FHH types 1 and 2 are due to germline loss-of-function mutations of the calcium-sensing receptor (CaSR) and G-protein subunit α-11 (Gα₁₁), respectively, whereas, FHH type 3 (FHH3) is mainly caused by germline heterozygous loss-of-function mutations affecting the Arg15 residue (Arg15Cys, Arg15His or Arg15Leu) of the adaptor-related protein complex 2-sigma subunit (AP2σ), which is encoded by the AP2S1 gene, and regulates CaSR endocytosis and endosomal signaling. FHH is considered to be an asymptomatic disorder characterised by mild-to-moderate hypercalcemia, normal or mildly elevated parathyroid hormone (PTH) concentrations and low urinary calcium excretion. However, some FHH3 patients, especially those harboring the Arg15Leu AP2S1 mutation, have marked and symptomatic hypercalcemia, thereby indicating that FHH3 may represent a more severe clinical disorder. To further evaluate the impact of the Arg15Leu AP2S1 mutation on calcium homeostasis, we utilised CRISPR/Cas9-mediated gene editing to generate C57BL/6J mice harboring the germline Arg15Leu mutation. Plasma and 24-hour urine samples were collected for biochemical analysis, and bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DEXA). All studies were conducted in mice aged 12-15 weeks (n = 10-12 mice per genotype), and in accordance with institutional welfare guidelines. Wild-type (Ap2s1^+/+), heterozygous (Ap2s1^+/L15) and homozygous (Ap2s1^L15/L15) mice were born as expected for a Mendelian pattern of inheritance, however, Ap2s1^L15/L15 mice died within 48 hours of birth. In contrast, male and female Ap2s1^+/L15mice were viable and biochemical analysis showed marked hypercalcemia (plasma albumin-adjusted calcium = 2.77±0.02 mmol/L) compared to wild-type (WT) mice (plasma albumin-adjusted calcium = 2.13±0.03 mmol/L, p<0.0001), and this finding was associated with significant hypophosphatemia and hypermagnesemia. Male and female Ap2s1^+/L15mice also had significant elevations of plasma PTH (157±14 pmol/L) compared to WT mice (63±10 pmol/L, p<0.0001). Furthermore, urine analysis showed that Ap2s1^+/L15mice were significantly hypocalciuric (fractional excretion of calcium (FECa) = 0.016±0.002) compared to WT mice (FECa =0.029±0.002, p<0.01), whilst, DEXA analysis demonstrated that Ap2s1^+/L15mice have significantly reduced BMD. Thus, these studies have established a mouse model for FHH3, which highlights the importance of the AP2σ protein in the parathyroid and renal regulation of mineral and bone homeostasis. In addition, these findings demonstrate that the germline heterozygous Arg15Leu AP2S1 mutation causes a severe form of FHH characterized by marked hypercalcemia, hyperparathyroidism and reduced BMD.

OR30-5 Germline Ablation of G-Protein Subunit Alpha-11 in Mice Causes Hypercalcemia That Is Rectified by Treatment with Cinacalcet

G-protein subunit α-₁₁ (Gα₁₁) is a signalling partner of the calcium-sensing receptor (CaSR), which is a G-protein coupled receptor that plays a major role in calcium homeostasis by regulating parathyroid hormone (PTH) secretion, urinary calcium excretion and skeletal development. Although loss-of-function point mutations of the GNA11 gene, which encodes Gα₁₁, have been shown to increase plasma calcium concentrations and cause familial hypocalciuric hypercalcemia type 2 (FHH2), the overall contribution of Gα₁₁ to the parathyroid, bone and renal regulation of calcium homeostasis remains to be established. The aim of this study was to characterise the impact of selective germline ablation of Gα₁₁ on plasma concentrations of albumin-adjusted calcium (adj-calcium) and PTH, 24-hour urinary calcium excretion, and bone mineral density (BMD) in adult male and female heterozygous and homozygous Gna11 null C57BL/6N mice (n=13-16 mice per genotype), which had been previously generated by the International Mouse Phenotyping Consortium (IMPC). These mice were also treated with cinacalcet to assess whether this CaSR positive allosteric modulator can rectify any alterations in calcium homeostasis. All studies were conducted in accordance with institutional welfare guidelines. Male and female heterozygous Gna11 null (Gna11^+/-) mice were viable and significantly hypercalcemic (plasma adj-calcium = 2.47±0.02 mM) compared to wild-type (WT) mice (plasma adj-calcium = 2.33±0.01 mM, p<0.0001). Gna11^+/- mice showed no alterations in plasma PTH or 24-hour urinary calcium. In contrast, homozygous Gna11 null (Gna11^-/-) mice showed reduced viability and the proportion of viable Gna11^-/- mice was >25% less than would be expected from a Mendelian pattern of inheritance (p=0.01, Chi-squared analysis). Moreover, male and female Gna11^-/- mice had significantly reduced body weight and were significantly more hypercalcemic (plasma adj-calcium = 2.70±0.02 mM) than Gna11^+/- or WT mice (p<0.0001). Female Gna11^-/- mice also showed significant increases in plasma PTH and 24-hour urinary calcium compared to female Gna11^+/- and WT mice. However, no alterations in BMD were observed in male and female Gna11^+/- or Gna11^-/- mice. Administration of a single oral 30mg/kg cinacalcet dose significantly reduced plasma adj-calcium and PTH in Gna11^+/- and Gna11^-/- mice, and normalised plasma adj-calcium concentrations in Gna11^-/- mice at 1-hour post-dose. Thus, these findings demonstrate that Gα₁₁ plays a major role in regulating plasma calcium concentrations, but does not influence BMD, nor represent a key mediator of urinary calcium excretion. Furthermore, cinacalcet rectifies the hypercalcemia of Gna11 null mice, thus indicating that this CaSR-targeted compound may modulate parathyroid gland function in a Gα₁₁-independent manner.

SAT-036 Extracellular Domain Calcium-Sensing Receptor (CaSR) Mutations Leading to Hypercalcemic and Hypocalcemic Disorders Cluster at the Homodimeric Interface

The calcium-sensing receptor (CaSR) is a homodimeric G-protein coupled receptor that plays a pivotal role in extracellular Ca²⁺ (Ca²⁺_e) homeostasis, and loss- and gain-of-function mutations of the CaSR cause familial hypocalciuric hypercalcemia type 1 (FHH1) and autosomal dominant hypocalcemia type 1 (ADH1), respectively. Crystal structure analysis has shown that the CaSR has a large extracellular domain (ECD) comprising lobes 1 and 2, and a cysteine-rich domain (CRD), which connects the ECD to the transmembrane domain. The CaSR ECD binds Ca²⁺_e at multiple sites, which induces conformational changes at the extracellular dimer interface that lead to intracellular signaling via the inositol trisphosphate (IP₃) and mitogen-activated protein kinase (MAPK) pathways. To further elucidate the structure-function relationships of the ECD, we examined the location of all CaSR ECD mutations reported to-date in FHH1 and ADH1 probands using available CaSR crystal structures. These studies identified that 127 FHH1 and 66 ADH1 mutations affected ECD residues, with >50% of these mutations being located at the dimer interface. Mutations predicted to disrupt key CaSR dimer-dimer interactions included: a lobe 1 Tyr161Cys mutation, which impaired an interprotomer interaction with the lobe 1 Pro55 residue; a Ser171Asn mutation predicted to disrupt a lobe 2 interprotomer salt bridge, which forms upon agonist binding; and a Gly553Arg mutation, which altered interprotomer hydrophobic interactions within the CRD. We investigated the effect of the Tyr161Cys, Ser171Asn and Gly553Arg mutations on receptor dimerization using western blotting and showed that these mutant proteins all form dimers similar to the wild-type (WT) CaSR. Furthermore, we evaluated the effect of these mutations on CaSR function in HEK293 cells following stimulation with Ca²⁺_e, by measuring accumulation of inositol monophosphate (IP₁), which is an IP₃ metabolite, and also by measuring serum response element (SRE)-containing luciferase reporter fold-change responses, which is an indicator of MAPK activation. The Tyr161Cys, Ser171Asn and Gly553Arg dimer interface mutations were shown to significantly impair CaSR-mediated signaling. Indeed, cells expressing the Tyr161Cys, Ser171Asn or Gly553Arg mutant CaSRs all showed a >30% reduction in IP₁ accumulation and >50% reduction in SRE-reporter responses, respectively, compared to WT-expressing cells (p<0.05, results are from 3 independent experiments). Thus, these studies demonstrate that the majority of FHH1- and ADH1-causing CaSR ECD mutations are located at the dimer interface, but likely do not disrupt dimer formation. Instead, these mutations may potentially influence conformational changes that occur at the dimer interface upon CaSR activation.

Standards of care for hypoparathyroidism in adults: a Canadian and International Consensus

PURPOSE

To provide practice recommendations for the diagnosis and management of hypoparathyroidism in adults.

METHODS

Key questions pertaining to the diagnosis and management of hypoparathyroidism were addressed following a literature review. We searched PubMed, MEDLINE, EMBASE and Cochrane databases from January 2000 to March 2018 using keywords 'hypoparathyroidism, diagnosis, treatment, calcium, PTH, calcidiol, calcitriol, hydrochlorothiazide and pregnancy'. Only English language papers involving humans were included. We excluded letters, reviews and editorials. The quality of evidence was evaluated based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. These standards of care for hypoparathyroidism have been endorsed by the Canadian Society of Endocrinology and Metabolism.

RESULTS

Hypoparathyroidism is a rare disease characterized by hypocalcemia, hyperphosphatemia and a low or inappropriately normal serum parathyroid hormone level (PTH). The majority of cases are post-surgical (75%) with nonsurgical causes accounting for the remaining 25% of cases. A careful review is required to determine the etiology of the hypoparathyroidism in individuals with nonsurgical disease. Hypoparathyroidism is associated with significant morbidity and poor quality of life. Treatment requires close monitoring as well as patient education. Conventional therapy with calcium supplements and active vitamin D analogs is effective in improving serum calcium as well as in controlling the symptoms of hypocalcemia. PTH replacement is of value in lowering the doses of calcium and active vitamin D analogs required and may be of value in lowering long-term complications of hypoparathyroidism. This manuscript addresses acute and chronic management of hypoparathyroidism in adults.

MAIN CONCLUSIONS

Hypoparathyroidism requires careful evaluation and pharmacologic intervention in order to improve serum calcium and control the symptoms of hypocalcemia. Frequent laboratory monitoring of the biochemical profile and patient education is essential to achieving optimal control of serum calcium.

Primary hyperparathyroidism: review and recommendations on evaluation, diagnosis, and management. A Canadian and international consensus

The purpose of this review is to assess the most recent evidence in the management of primary hyperparathyroidism (PHPT) and provide updated recommendations for its evaluation, diagnosis and treatment. A Medline search of "Hyperparathyroidism. Primary" was conducted and the literature with the highest levels of evidence were reviewed and used to formulate recommendations. PHPT is a common endocrine disorder usually discovered by routine biochemical screening. PHPT is defined as hypercalcemia with increased or inappropriately normal plasma parathyroid hormone (PTH). It is most commonly seen after the age of 50 years, with women predominating by three to fourfold. In countries with routine multichannel screening, PHPT is identified earlier and may be asymptomatic. Where biochemical testing is not routine, PHPT is more likely to present with skeletal complications, or nephrolithiasis. Parathyroidectomy (PTx) is indicated for those with symptomatic disease. For asymptomatic patients, recent guidelines have recommended criteria for surgery, however PTx can also be considered in those who do not meet criteria, and prefer surgery. Non-surgical therapies are available when surgery is not appropriate. This review presents the current state of the art in the diagnosis and management of PHPT and updates the Canadian Position paper on PHPT. An overview of the impact of PHPT on the skeleton and other target organs is presented with international consensus. Differences in the international presentation of this condition are also summarized.

Cox-2 promotes chromogranin A expression and bioactivity: evidence for a prostaglandin E2-dependent mechanism and the involvement of a proximal cyclic adenosine 5'-monophosphate-responsive element

The prostanoid biosynthetic enzyme cyclooxygenase-2 (Cox-2) is up-regulated in several neuroendocrine tumors. The aim of the current study was to employ a neuroendocrine cell (PC12) model of Cox-2 overexpression to identify gene products that might be implicated in the oncogenic and/or inflammatory actions of this enzyme in the setting of neuroendocrine neoplasia. Expression array and real-time PCR analysis demonstrated that levels of the neuroendocrine marker chromogranin A (CGA) were 2- and 3.2-fold higher, respectively, in Cox-2 overexpressing cells (PCXII) vs. their control (PCMT) counterparts. Immunocytochemical and immunoblotting analyses confirmed that both intracellular and secreted levels of CGA were elevated in response to Cox-2 induction. Moreover, exogenous addition of prostaglandin E(2) (1 microm) mimicked this effect in PCMT cells, whereas treatment of PCXII cells with the Cox-2 selective inhibitor NS-398 (100 nm) reduced CGA expression levels, thereby confirming the biospecificity of this finding. Levels of neuron-specific enolase were similar in the two cell lines, suggesting that the effect of Cox-2 on CGA expression was specific and not due to a global enhancement of neuroendocrine marker expression/differentiation. Cox-2-dependent CGA up-regulation was associated with significantly increased chromaffin granule number and intracellular and secreted levels of dopamine. CGA promoter-driven reporter gene expression studies provided evidence that prostaglandin E(2)-dependent up-regulation required a proximal cAMP-responsive element (-71 to -64 bp). This study is the first to demonstrate that Cox-2 up-regulates both CGA expression and bioactivity in a neuroendocrine cell line and has major implications for the role of this polypeptide in the pathogenesis of neuroendocrine cancers in which Cox-2 is up-regulated.

Lymphatic vessels are present in phosphaturic mesenchymal tumours

Oncogenic osteomalacia (OO) is an acquired form of hypophosphataemic osteomalacia, which is associated most commonly with the development of a benign phosphaturic mesenchymal tumour mixed connective tissue type (PMTMCT). PMTMCTs are generally well vascularised tumours, and many have in the past been classified as haemangiomas and haemangiopericytomas. Although these tumours show some morphological variation, it has been proposed that they represent a distinct histopathological entity. Our aim in this study was to determine by immunohistochemistry the vascular profile of PMTMCT. Using monoclonal antibodies directed against several vascular markers, including the lymphatic endothelial cell antigens LYVE 1 and podoplanin, we found that PMTMCTs, in contrast to haemangiomas and haemangiopericytomas, contain lymphatic vessels. Taken with previous observations that PMTMCTs overexpress FGF23 and other gene products, this finding provides further evidence that most osteomalacia associated mesenchymal tumours represent a discrete pathological entity.

Neonatal severe hyperparathyroidism: genotype/phenotype correlation and the use of pamidronate as rescue therapy

Familial hypocalciuric hypercalcaemia (FHH) is an autosomal dominant condition due to heterozygous loss of function calcium sensing receptor (CaSR) mutations. However, individuals who are homozygous for CaSR mutations have neonatal severe hyperparathyroidism (NSHPT), which unlike the relatively benign and asymptomatic FHH can be fatal without parathyroidectomy. We report three patients with NSHPT associated with marked hypercalcaemia and severe hyperparathyroidism with related skeletal demineralisation. We describe the novel use of intravenous pamidronate in NSHPT, to control severe hypercalcaemia in these patients prior to parathyroidectomy and in one individual as a rescue therapy to stabilise life-threatening demineralisation. Furthermore, a marked phenotypic heterogeneity was observed amongst four members from a large kindred with the same homozygous CaSR mutations: one patient would have died without parathyroidectomy in infancy; a second patient survived infancy but underwent parathyroidectomy in early childhood following severe symptomatic hypercalcaemic episodes; whilst the other two patients have survived to adolescence without parathyroidectomy. Additionally, in contrast to the literature these two individuals suffered minimal morbidity.

CONCLUSION

We commend the short-term use of pamidronate in neonatal severe hyperparathyroidism to treat extreme hypercalcaemia and halt hyperparathyroid-driven skeletal demineralisation in preparation for parathyroidectomy. The remarkable degree of phenotypic variation demonstrated remains unexplained without functional studies; this variability highlights the challenge of treating this rare condition.

Dent's disease--a nephrolithiasis disorder associated with defective receptor-mediated endocytosis

Dent's disease, a renal tubular disorder characterized by low-molecular-weight proteinuria (LMWP), hypercalciuria, and nephrolithiasis, is due to inactivating mutations in the x-linked renal specific chloride channel CLC-5. CLC-5 belongs to the family of voltage-gated chloride channels, which function as homodimeric proteins with each subunit consisting of 18 helices and a chloride selectivity filter, i.e. pore. None of the 15 CLC-5 missense mutations reported in patients with dent's disease involves the chloride selectivity filter, but 12 of these are clustered around the interface of the two subunits, thereby emphasising the important role for the interaction between the two subunits at the interface of the homodimeric CLC-5. In the kidney, CLC-5 forms part of the receptor-mediated endocytic pathway, and defects in this pathway due to a loss of CLC-5 function, may help to account for the LMWP, hyperphosphaturia, hypercalciuria and nephrolithiasis. The molecular studies and the generation of mouse models of the disease have increased our understanding of the renal tubular mechanisms that regulate mineral homeostasis.

Bardet-Biedl syndrome: a molecular and phenotypic study of 18 families

The autosomal recessive disorder Bardet-Biedl syndrome is characterised by retinal degeneration, polydactyly, obesity, mental retardation, hypogenitalism, renal dysplasia, and short stature. It is heterogeneous with at least four gene loci (BBS1-4) having been mapped to date. We have studied 18 multiply affected families noting the presence of both major and minor manifestations. Using a fluorescently based PCR technique, we genotyped each family member and assigned linkage to one of the four loci. Given this degree of heterogeneity we hoped to find phenotypic differences between linkage categories. We found 44% of families linked to 11q13 (BBS1) and 17% linked to 16q21 (BBS2). Only one family was linked to 15q22 (BBS4) and none to 3p12. We conclude that BBS1 is the major locus among white Bardet-Biedl patients and that BBS3 is extremely rare. Only subtle phenotypic differences were observed, the most striking of which was a finding of taller affected offspring compared with their parents in the BBS1 category. Affected subjects in the BBS2 and 4 groups were significantly shorter than their parents. Twenty eight percent of pedigrees did not show linkage to any known locus, evidence for at least a fifth gene. We conclude that the different genes responsible for Bardet-Biedl syndrome may influence growth characteristics such as height.

Value of routine chest radiography in an acute geriatric unit

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Anthropometric measurements in patients with growth hormone deficiency before treatment with human growth hormone

In 74 children (52 males, 22 females) with growth hormone (GH) deficiency (30 cases with isolated GH-deficiency, two of them familial; 4 familial and one isolated case with tendency for formation of antibodies against hGH; 29 with other pituitary hormone defects; 10 craniopharyngiomas), various anthropometric measurements were analyzed before treatment with hGH. In all groups, standing height, sitting height, and subischial leg height were equally retarded, and bihumeral width was more retarded than biiliac width; the head was relatively large; fat tissue was increased with subscapular skinfolds being greater than triceps skinfolds, indicating relative obestiy of the trunk; muscle and/or bone mass was reduced. In isolated GH-deficiency, head shape was slightly scaphoid; in combined defects, it was round, and in craniopharyngioma cases, it was brachycephalic. It is concluded that antrhopometric measurements may help in differentiating the type of GH-deficiency.