Paul Dimitri

Obesity is a risk factor for fracture in children but is protective against fracture in adults: A paradox

With the rise in obesity worldwide, an important debate has developed as to whether excess fat has a detrimental or protective effect on skeletal health in children and adults. Obese children appear to be over represented in fracture groups and recent evidence suggests that fat may be detrimental to bone accrual in children, although this effect may be confined to adolescence during rapid skeletal growth. Fat induced alterations in hormonal factors and cytokines during growth may play a pivotal role in disturbing bone accrual. In contrast, the widely accepted opinion is that fat appears to be protective of bone in adults and minimises bone loss in postmenopausal women. Recent evidence suggests that in adults, site specific fat depots may exert differing effects on bone (with visceral fat acting as a pathogenic fat depot and subcutaneous fat exerting protective effects), and that the effects of fat mass on bone and fracture risk may vary by skeletal site; obesity protects against hip and vertebral fractures but is a risk factor for fractures of the humerus and ankle. The incidence of fracture during adolescence is rising and osteoporosis remains a considerable health burden in older adults. Understanding the effects of fat mass on bone during growth and early adulthood is vital in informing future health strategies and pharmacotherapies to optimise peak bone mass and prevent fracture.

Fat and bone in children: Differential effects of obesity on bone size and mass according to fracture history

Fat mass predicts bone accrual in prepubertal children, but obese children have increased fracture risk. We hypothesised that bone size and mass would vary according to prior fracture in obese children. One hundred and three children (52 obese) underwent dual‐energy X‐ray absorptiometry (DXA) scanning of the lumbar spine, total body, and radial metaphysis and diaphysis. We derived body size–adjusted bone mineral density (BMD) estimates for each site using commonly employed procedures. Following adjustment for either age, age2 and weight, or height and weight based on a reference group of nonobese controls without previous fracture, obese children with prior fracture showed a 0.8 to 1.2 SD reduction in total body areal BMD (aBMD), a 3.0 SD decrease in lumbar (L2–4) aBMD, and a 2.0 SD reduction in radial shaft aBMD. These changes were significant at p < .005. Lumbar volumetric BMD (vBMD) calculated by Carter and Kröger algorithms was significantly reduced in obese children with prior fracture (2.0 to 3.3 SD). Eighteen percent of obese children fulfilled the criteria for osteoporosis. Despite greater lean mass for height in obese children (p < .0001), total body bone mineral content (BMC) for lean mass was reduced (p = .002). Multiple regression models adjusting for height, weight, and gender demonstrated an inverse relationship between total body fat mass and total body, lumbar, and ultradistal radius BMC and aBMD. The data suggest that fat mass substantially inhibits bone accrual in children with prior fracture. These children may require targeted interventions to increase bone mass during adolescence to achieve optimal peak bone mass and reduce the risk of osteoporosis later in life.

Adipokines, bone-derived factors and bone turnover in obese children; evidence for altered fat-bone signalling resulting in reduced bone mass

UNLABELLED Obese children, particularly those who have fractured, have reduced body size-adjusted total body and regional bone mass. We performed an observational cross-sectional cohort study to determine the relationship between adipokines (leptin and adiponectin), bone-derived cytokines and bone turnover in children which may explain this observation. Participants aged 5-16 years were recruited into obese (BMI SDS 3.3±0.6) and lean (BMI SDS 0.2±1.0) groups and further subdivided into groups by fracture history. Free leptin (leptin/leptin soluble receptor) and adiponectin; RANK-ligand (RANKL), osteoprotegerin (OPG); Dickkopf-1 (DKK1); and the bone turnover markers procollagen type I amino propeptide (P1NP) and carboxy-terminal telopeptide of type I collagen (CTx). Total body and truncal fat mass were measured by DXA. RESULTS Free leptin (p>0.0001) and adiponectin (p=0.0002) were higher and lower in obese children respectively. OPG was lower in obese children (p=0.01), being inversely related to free leptin (p=0.009), total body and truncal fat mass (both p=0.01). RANKL was inversely related to free leptin in children with prior fracture (p=0.03). CTx was higher in obese children (p=0.003). Free leptin was positively associated with both CTx (p=0.03) and P1NP (p=0.02). DKK1 was inversely related to adiponectin (p=0.02). CONCLUSION Bone formation relative to resorption was reduced in obese children; this difference was accentuated in those with prior fracture. Adipokines may regulate these changes. Osteoprotegerin may play a fundamental role in the failure of obese children to accrue bone mass appropriately.

Novel GLIS3 mutations demonstrate an extended multisystem phenotype

INTRODUCTION Mutations in the GLI-similar 3 (GLIS3) gene encoding the transcription factor GLIS3 are a rare cause of neonatal diabetes and congenital hypothyroidism with six affected cases from three families reported to date. Additional features, described previously, include congenital glaucoma, hepatic fibrosis, polycystic kidneys, developmental delay and facial dysmorphism. SUBJECTS We report two new cases from unrelated families with distinct novel homozygous partial GLIS3 deletions. Both patients presented with neonatal diabetes mellitus, severe resistant hypothyroidism in the presence of elevated thyroglobulin and normal thyroid anatomy, degenerative liver disease, cystic renal dysplasia, recurrent infections and facial dysmorphism. These novel mutations have also resulted in osteopenia, bilateral sensorineural deafness and pancreatic exocrine insufficiency, features that have not previously been associated with GLIS3 mutations. Gene dosage analysis showed that the parents were carriers of a deletion encompassing exons 1-2 (case 1) or exons 1-4 (case 2) of the 11 exon gene. Genome-wide SNP analysis did not reveal a common ancestral GLIS3 haplotype in patient 2. CONCLUSIONS Our results confirm partial gene deletions as the most common type of GLIS3 mutations, accounting for four of five families identified to date. We propose that mutations in GLIS3 lead to a wider clinical phenotype than previously recognised. We also report the first case of a recessive GLIS3 mutation causing neonatal diabetes and congenital hypothyroidism in a child from a non-consanguineous pedigree, highlighting the importance of molecular genetic testing in any patient with this phenotype.

Somatic mutations and progressive monosomy modify SAMD9 -related phenotypes in humans

It is well established that somatic genomic changes can influence phenotypes in cancer, but the role of adaptive changes in developmental disorders is less well understood. Here we have used next-generation sequencing approaches to identify de novo heterozygous mutations in sterile &agr; motif domain–containing protein 9 (SAMD9, located on chromosome 7q21.2) in 8 children with a multisystem disorder termed MIRAGE syndrome that is characterized by intrauterine growth restriction (IUGR) with gonadal, adrenal, and bone marrow failure, predisposition to infections, and high mortality. These mutations result in gain of function of the growth repressor product SAMD9. Progressive loss of mutated SAMD9 through the development of monosomy 7 (–7), deletions of 7q (7q–), and secondary somatic loss-of-function (nonsense and frameshift) mutations in SAMD9 rescued the growth-restricting effects of mutant SAMD9 proteins in bone marrow and was associated with increased length of survival. However, 2 patients with –7 and 7q– developed myelodysplastic syndrome, most likely due to haploinsufficiency of related 7q21.2 genes. Taken together, these findings provide strong evidence that progressive somatic changes can occur in specific tissues and can subsequently modify disease phenotype and influence survival. Such tissue-specific adaptability may be a more common mechanism modifying the expression of human genetic conditions than is currently recognized.

Expanding the Clinical Spectrum Associated With GLIS3 Mutations

Context: GLIS3 (GLI-similar 3) is a member of the GLI-similar zinc finger protein family encoding for a nuclear protein with 5 C2H2-type zinc finger domains. The protein is expressed early in embryogenesis and plays a critical role as both a repressor and activator of transcription. Human GLIS3 mutations are extremely rare. Objective: The purpose of this article was determine the phenotypic presentation of 12 patients with a variety of GLIS3 mutations. Methods: GLIS3 gene mutations were sought by PCR amplification and sequence analysis of exons 1 to 11. Clinical information was provided by the referring clinicians and subsequently using a questionnaire circulated to gain further information. Results: We report the first case of a patient with a compound heterozygous mutation in GLIS3 who did not present with congenital hypothyroidism. All patients presented with neonatal diabetes with a range of insulin sensitivities. Thyroid disease varied among patients. Hepatic and renal disease was common with liver dysfunction ranging from hepatitis to cirrhosis; cystic dysplasia was the most common renal manifestation. We describe new presenting features in patients with GLIS3 mutations, including craniosynostosis, hiatus hernia, atrial septal defect, splenic cyst, and choanal atresia and confirm further cases with sensorineural deafness and exocrine pancreatic insufficiency. Conclusion: We report new findings within the GLIS3 phenotype, further extending the spectrum of abnormalities associated with GLIS3 mutations and providing novel insights into the role of GLIS3 in human physiological development. All but 2 of the patients within our cohort are still alive, and we describe the first patient to live to adulthood with a GLIS3 mutation, suggesting that even patients with a severe GLIS3 phenotype may have a longer life expectancy than originally described.

An emerging, recognizable facial phenotype in association with mutations in GLI‐similar 3 (GLIS3)

Neonatal diabetes and hypothyroidism (NDH) syndrome was first described in 2003 in a consanguineous Saudi Arabian family where two out of four siblings were reported to have presented with proportionate IUGR, neonatal non‐autoimmune diabetes mellitus, severe congenital hypothyroidism, cholestasis, congenital glaucoma, and polycystic kidneys. Liver disease progressed to hepatic fibrosis. The renal disease was characterized by enlarged kidneys and multiple small cysts with deficient cortico‐medullary junction differentiation and normal kidney function. There was minor facial dysmorphism (depressed nasal bridge, large anterior fontanelle, long philtrum) reported but no facial photographs were published. Mutations in the transcription factor GLI‐similar 3 (GLIS3) gene in the original family and two other families were subsequently reported in 2006. All affected individuals had neonatal diabetes, congenital hypothyroidism but glaucoma and liver and kidney involvement were less consistent features. Detailed descriptions of the facial dysmorphism have not been reported previously. In this report, we describe the common facial dysmorphism consisting of bilateral low‐set ears, depressed nasal bridge with overhanging columella, elongated, upslanted palpebral fissures, persistent long philtrum with a thin vermilion border of the upper lip in a cohort of seven patients with GLIS3 mutations and report the emergence of a distinct, probably recognizable facial gestalt in this group which evolves with age.

Xanthogranulomatous hypophysitis: a rare and often mistaken pituitary lesion

Summary Xanthogranulomatous hypophysitis (XGH) is a very rare form of pituitary hypophysitis that may present both clinically and radiologically as a neoplastic lesion. It may either be primary with an autoimmune aetiology and can occur in isolation or as a part of autoimmune systemic disease or secondary as a reactive degenerative response to an epithelial lesion (e.g. craniopharyngioma (CP), Rathkes cleft cyst, germinoma and pituitary adenomas) or as a part of a multiorgan systemic involvement such as tuberculosis, sarcoidosis or granulomatosis. It may also present with a variation of symptoms in children and adults. Our case series compares the paediatric and adult presentations of XGH and the differential diagnoses considered in one child and two adult patients, highlighting the wide spectrum of this condition. Endocrine investigations suggested panhypopituitarism in all three patients and imaging revealed a suprasellar mass compressing the optic chiasm suggestive of CP or Rathkes cleft cyst in one patient and non-functioning pituitary macroadenoma in two patients. Magnetic resonance imaging (MRI) demonstrated mixed signal intensities on T1- and T2-weighted sequences. Following endoscopic transsphenoidal surgery, histological analysis revealed necrotic material with a xanthogranulomatous reaction confirming XGH in two patients and a necrobiotic granulomatous chronic inflammatory infiltrate with neutrophils in one patient, which is not typical of current descriptions of this disorder. This case series describes the wide spectrum of XGH disease that is yet to be defined. Mixed signal intensities on T1- and T2-weighted MRI sequences may indicate XGH and diagnosis is confirmed by histology. Histological variation may indicate an underlying systemic process. Learning points XGH is a rare form of pituitary hypophysitis with a wide clinical and histological spectrum and can mimic a neoplastic lesion. XGH primarily presents with growth arrest in children and pubertal arrest in adolescents. In adults, the presentation may vary. A combination of hypopituitarism and mixed signal intensity lesion on MRI is suggestive of XGH and should be considered in the differential diagnosis of sellar lesions. Radical surgery is the treatment of choice and carries an excellent prognosis with no recurrence.

Pituitary tumour apoplexy within prolactinomas in children: a more aggressive condition?

ObjectivesTo evaluate clinical presentations, diagnosis and management of paediatric patients presenting with pituitary apoplexy.MethodsA retrospective case series describing a cohort of paediatric patients presenting with this condition from 2010–2016 to a tertiary referral children’s hospital in the United Kingdom.ResultsPituitary apoplexy is a rare condition that seems to have a higher relative incidence in children than adults. Our series suggests that pituitary apoplexy in paediatric patients with adenomas appears more common than previously described. All our patients required surgery, either as an acute or delayed procedure, for visual compromise. Two patients had commenced growth hormone (GH) for GH deficiency two weeks prior to the onset of pituitary apoplexy.ConclusionsWith only a limited number of published case reports surrounding this topic our case series contributes to help further understand and manage this condition.

Borderline peak plasma cortisol following Synacthen stimulation - single-centre analysis of three years' data

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