Evaluation of 100 Dutch cases with 16p11.2 deletion and duplication syndromes; from clinical manifestations towards personalized treatment options

The 16p11.2 deletion syndrome is a clinically heterogeneous disorder, characterized by developmental delay, intellectual disability, hyperphagia, obesity, macrocephaly and psychiatric problems. Cases with 16p11.2 duplication syndrome have similar neurodevelopmental problems, but typically show a partial 'mirror phenotype' with underweight and microcephaly. Various copy number variants (CNVs) of the chromosomal 16p11.2 region have been described. Most is known about the 'typical' 16p11.2 BP4-BP5 (29.6-30.2 Mb; ~600 kb) deletions and duplications, but there are also several published cohorts with more distal 16p11.2 BP2-BP3 CNVs (28.8-29.0 Mb; ~220 kb), who exhibit clinical overlap. We assessed 100 cases with various pathogenic 16p11.2 CNVs and compared their clinical characteristics to provide more clear genotype-phenotype correlations and raise awareness of the different 16p11.2 CNVs. Neurodevelopmental and weight issues were reported in the majority of cases. Cases with distal 16p11.2 BP2-BP3 deletion showed the most severe obesity phenotype (73.7% obesity, mean BMI SDS 3.2). In addition to the more well defined typical 16p11.2 BP4-BP5 and distal 16p11.2 BP2-BP3 CNVs, we describe the clinical features of five cases with other, overlapping, 16p11.2 CNVs in more detail. Interestingly, four cases had a second genetic diagnosis and 18 cases an additional gene variant of uncertain significance, that could potentially help explain the cases' phenotypes. In conclusion, we provide an overview of our Dutch cohort of cases with various pathogenic 16p11.2 CNVs and relevant second genetic findings, that can aid in adequately recognizing, diagnosing and counseling of individuals with 16p11.2 CNVs, and describe the personalized medicine for cases with these conditions.

IMPROVE 2022 International Meeting on Pathway-Related Obesity: Vision of Excellence

Nearly 90 clinicians and researchers from around the world attended the first IMPROVE 2022 International Meeting on Pathway-Related Obesity. Delegates attended in person or online from across Europe, Argentina and Israel to hear the latest scientific and clinical developments in hyperphagia and severe, early-onset obesity, and set out a vision of excellence for the future for improving the diagnosis, treatment, and care of patients with melanocortin-4 receptor (MC4R) pathway-related obesity. The meeting co-chair Peter Kühnen, Charité Universitätsmedizin Berlin, Germany, indicated that change was needed with the rapidly increasing prevalence of obesity and the associated complications to improve the understanding of the underlying mechanisms and acknowledge that monogenic forms of obesity can play an important role, providing insights that can be applied to a wider group of patients with obesity. World-leading experts presented the latest research and led discussions on the underlying science of obesity, diagnosis (including clinical and genetic approaches such as the role of defective MC4R signalling), and emerging clinical data and research with targeted pharmacological approaches. The aim of the meeting was to agree on the questions that needed to be addressed in future research and to ensure that optimised diagnostic work-up was used with new genetic testing tools becoming available. This should aid the planning of new evidence-based treatment strategies for the future, as explained by co-chair Martin Wabitsch, Ulm University Medical Center, Germany.

GNB1 and obesity: Evidence for a correlation between haploinsufficiency and syndromic obesity

Most patients with GNB1 encephalopathy have developmental delay and/or intellectual disability, brain anomalies and seizures. Recently, two cases with GNB1 encephalopathy caused by haploinsufficiency have been reported that also show a Prader-Willi-like phenotype of childhood hypotonia and severe obesity. Here we present three new cases from our expert centre for genetic obesity in which GNB1 truncating and splice variants, probably leading to haploinsufficiency, were identified. They all have obesity, hyperphagia and intellectual deficit. The clinical cases and their weight courses are presented, together with a review of all 68 published cases with GNB1 encephalopathy. Information on weight was not mentioned in most of these articles, so we contacted authors for additional clinical information on weight status and hyperphagia. Of the 42 patients whose weight status we could determine, obesity was present in 8 patients (19%). Obesity is significantly over-represented in the group with truncating and splicing variants. In this group, we see an obesity prevalence of 75%. Since GNB1 has been linked to several key genes in the hypothalamic leptin-melanocortin pathway, which regulates satiety and energy expenditure, our data support the potential association between GNB1 haploinsufficiency and genetic obesity. We also suggest GNB1 is a candidate gene for the known obesity phenotype of the 1p36 microdeletion syndrome given this chromosomal region includes the GNB1 gene. Knowledge of an additional obesity phenotype is important for prognosis, early interventions against obesity and awareness when prescribing weight-inducing medication.

Developmental epileptic encephalopathy in DLG4-related synaptopathy

OBJECTIVE

The postsynaptic density protein of excitatory neurons PSD-95 is encoded by discs large MAGUK scaffold protein 4 (DLG4), de novo pathogenic variants of which lead to DLG4-related synaptopathy. The major clinical features are developmental delay, intellectual disability (ID), hypotonia, sleep disturbances, movement disorders, and epilepsy. Even though epilepsy is present in 50% of the individuals, it has not been investigated in detail. We describe here the phenotypic spectrum of epilepsy and associated comorbidities in patients with DLG4-related synaptopathy.

METHODS

We included 35 individuals with a DLG4 variant and epilepsy as part of a multicenter study. The DLG4 variants were detected by the referring laboratories. The degree of ID, hypotonia, developmental delay, and motor disturbances were evaluated by the referring clinician. Data on awake and sleep electroencephalography (EEG) and/or video-polygraphy and brain magnetic resonance imaging were collected. Antiseizure medication response was retrospectively assessed by the referring clinician.

RESULTS

A large variety of seizure types was reported, although focal seizures were the most common. Encephalopathy related to status epilepticus during slow-wave sleep (ESES)/developmental epileptic encephalopathy with spike-wave activation during sleep (DEE-SWAS) was diagnosed in >25% of the individuals. All but one individual presented with neurodevelopmental delay. Regression in verbal and/or motor domains was observed in all individuals who suffered from ESES/DEE-SWAS, as well as some who did not. We could not identify a clear genotype-phenotype relationship even between individuals with the same DLG4 variants.

SIGNIFICANCE

Our study shows that a subgroup of individuals with DLG4-related synaptopathy have DEE, and approximately one fourth of them have ESES/DEE-SWAS. Our study confirms DEE as part of the DLG4-related phenotypic spectrum. Occurrence of ESES/DEE-SWAS in DLG4-related synaptopathy requires proper investigation with sleep EEG.

Mirror Hand Movements Caused by a Deletion of the DCC Gene

This case report describes the evaluation of 16-year-old twins with chromosomal microarray and mirror movements.

Delineation of the adult phenotype of Coffin-Siris syndrome in 35 individuals

Coffin-Siris syndrome (CSS) is a rare multisystemic autosomal dominant disorder. Since 2012, alterations in genes of the SWI/SNF complex were identified as the molecular basis of CSS, studying largely pediatric cohorts. Therefore, there is a lack of information on the phenotype in adulthood, particularly on the clinical outcome in adulthood and associated risks. In an international collaborative effort, data from 35 individuals ≥ 18 years with a molecularly ascertained CSS diagnosis (variants in ARID1B, ARID2, SMARCA4, SMARCB1, SMARCC2, SMARCE1, SOX11, BICRA) using a comprehensive questionnaire was collected. Our results indicate that overweight and obesity are frequent in adults with CSS. Visual impairment, scoliosis, and behavioral anomalies are more prevalent than in published pediatric or mixed cohorts. Cognitive outcomes range from profound intellectual disability (ID) to low normal IQ, with most individuals having moderate ID. The present study describes the first exclusively adult cohort of CSS individuals. We were able to delineate some features of CSS that develop over time and have therefore been underrepresented in previously reported largely pediatric cohorts, and provide recommendations for follow-up.

Genetic Obesity Disorders: Body Mass Index Trajectories and Age of Onset of Obesity Compared with Children with Obesity from the General Population

OBJECTIVE

We sought to assess body mass index trajectories of children with genetic obesity to identify optimal early age of onset of obesity (AoO) cut-offs for genetic screening.

STUDY DESIGN

This longitudinal, observational study included growth measurements from birth onward of children with nonsyndromic and syndromic genetic obesity and control children with obesity from a population-based cohort. Diagnostic performance of AoO was evaluated.

RESULTS

We describe the body mass index trajectories of 62 children with genetic obesity (29 nonsyndromic, 33 syndromic) and 298 controls. Median AoO was 1.2 years in nonsyndromic genetic obesity (0.4 and 0.6 years in biallelic LEPR and MC4R; 1.7 in heterozygous MC4R); 2.0 years in syndromic genetic obesity (0.9, 2.3, 4.3, and 6.8 years in pseudohypoparathyroidism, Bardet-Biedl syndrome, 16p11.2del syndrome, and Temple syndrome, respectively); and 3.8 years in controls. The optimal AoO cut-off was ≤3.9 years (sensitivity, 0.83; specificity, 0.49; area under the curve, 0.79; P < .001) for nonsyndromic and ≤4.7 years (sensitivity, 0.82; specificity, 0.37; area under the curve, 0.68; P = .001) for syndromic genetic obesity.

CONCLUSIONS

Optimal AoO cut-off as single parameter to determine which children should undergo genetic testing was ≤3.9 years. In case of older AoO, additional features indicative of genetic obesity should be present to warrant genetic testing. Optimal cut-offs might differ across different races and ethnicities.

The Narrative of a Patient with Leptin Receptor Deficiency: Personalized Medicine for a Rare Genetic Obesity Disorder

Leptin receptor (LEPR) deficiency is a rare genetic disorder that affects the body's ability to regulate appetite and weight. For patients and their families, the disorder seriously disrupts daily life; however, little is published about this impact. We here report the experiences of a 10.5-year-old girl with leptin receptor deficiency and her family. The diagnosis of this rare genetic obesity had a deep impact on the life of the child and her family. It led to a better understanding of the cause of the impaired appetite regulation and early-onset obesity with subsequently less judgement by others and improved cooperation of their social network and school on maintaining a healthy lifestyle for this girl. A strict eating regimen and lifestyle measures resulted in the first year after diagnosis in a significantly decreased body mass index (BMI), followed by BMI stabilization, still categorized as obesity class three. However, the troublesome challenge of how to manage the disruptive behaviour due to hyperphagia remained. Eventually, due to treatment with targeted pharmacotherapy, i.e., melanocortin-4 receptor agonists, her BMI continued to decrease due to resolving hyperphagia. The daily routine of the family and the atmosphere at home positively changed as they were no longer dominated by the food-focused behaviour of the child and the adherence to the strict eating regimen. This case report demonstrates the importance and impact of a rare genetic obesity disorder diagnosis in a family. Additionally, it highlights the value of genetic testing in patients with a high suspicion of a genetic obesity disorder as it can eventually lead to personalized treatment, such as guidance by specialized healthcare professionals and educated caregivers or targeted pharmacotherapy.

Obesity and Hyperphagia With Increased Defective ACTH: A Novel POMC Variant

OBJECTIVE

Patients with pro-opiomelanocortin (POMC) defects generally present with early-onset obesity, hyperphagia, hypopigmentation and adrenocorticotropin (ACTH) deficiency. Rodent models suggest that adequate cleavage of ACTH to α-melanocortin-stimulating hormone (α-MSH) and desacetyl-α-melanocortin-stimulating hormone (d-α-MSH) by prohormone convertase 2 at the KKRR region is required for regulating food intake and energy balance.

METHODS

We present 2 sisters with a novel POMC gene variant, leading to an ACTH defect at the prohormone convertase 2 cleavage site, and performed functional studies of this variant.

RESULTS

The patients had obesity, hyperphagia and hypocortisolism, with markerly raised levels of ACTH but unaffected pigmentation. Their ACTH has reduced potency to stimulate the melanocortin (MC) 2 receptor, explaining their hypocortisolism.

CONCLUSION

The hyperphagia and obesity support evidence that adequate cleavage of ACTH to α-MSH and d-α-MSH is also required in humans for feeding control.

SOX11 variants cause a neurodevelopmental disorder with infrequent ocular malformations and hypogonadotropic hypogonadism and with distinct DNA methylation profile

PURPOSE

This study aimed to undertake a multidisciplinary characterization of the phenotype associated with SOX11 variants.

METHODS

Individuals with protein altering variants in SOX11 were identified through exome and genome sequencing and international data sharing. Deep clinical phenotyping was undertaken by referring clinicians. Blood DNA methylation was assessed using Infinium MethylationEPIC array. The expression pattern of SOX11 in developing human brain was defined using RNAscope.

RESULTS

We reported 38 new patients with SOX11 variants. Idiopathic hypogonadotropic hypogonadism was confirmed as a feature of SOX11 syndrome. A distinctive pattern of blood DNA methylation was identified in SOX11 syndrome, separating SOX11 syndrome from other BAFopathies.

CONCLUSION

SOX11 syndrome is a distinct clinical entity with characteristic clinical features and episignature differentiating it from BAFopathies.

Impact of the COVID-19 Pandemic and Related Lockdown Measures on Lifestyle Behaviors and Well-Being in Children and Adolescents with Severe Obesity

INTRODUCTION

COVID-19 lockdown measures have large impact on lifestyle behaviors and well-being of children. The aim of this mixed-methods study was to investigate the impact of COVID-19 lockdown measures on eating styles and behaviors, physical activity (PA), screen time, and health-related quality of life (HRQoL) in children (0-18 years) with severe obesity.

METHODS

During the first COVID-19 wave (April 2020), validated questionnaires were completed and semi-structured telephone interviews were conducted with parents of children with severe obesity (adult body mass index [BMI]-equivalent ≥35 kg/m2) and/or with the children themselves. Changes in pre-pandemic versus lockdown scores of the Dutch Eating Behavior Questionnaire Children, Pediatric Quality of Life Inventory, and Dutch PA Questionnaire were assessed. Qualitative analyses were performed according to the Grounded Theory.

RESULTS

Ninety families were approached of which 83 families were included. Characteristics of the included children were: mean age 11.2 ± 4.6 years, 52% female, mean BMI SD-score +3.8 ± 1.0. Emotional, restrained, and external eating styles, HRQoL, and (noneducational) screen time did not change on group level (all p > 0.05). However, weekly PA decreased (mean difference -1.9 h/week, p = 0.02) mostly in adolescents. In the majority of children, mean weekly PA decreased to ≤2 h/week. Children with high emotional or external eating scores during lockdown or pre-existent psychosocial problems had the lowest HRQoL (p < 0.01). Qualitative analyses revealed an increased demand for food in a significant proportion of children (n = 21), mostly in children <10 years (19/21). This was often attributed to loss of daily structure and perceived stress. Families who reported no changes (n = 15) or improved eating behaviors (n = 11) attributed this to already existing strict eating schemes that they kept adhering to during lockdown.

CONCLUSION

This study shows differing responses to COVID-19 lockdown measures in children with severe obesity. On group level, PA significantly decreased and in substantial minorities eating styles and HRQoL deteriorated. Children with pre-existent psychosocial problems or pre-pandemic high external or emotional eating scores were most at risk. These children and their families should be targeted by health care professionals to minimize negative physical and mental health consequences.

Effects of glucagon-like peptide-1 analogue treatment in genetic obesity: A case series

Obesity is highly prevalent and comes with serious health burden. In a minority, a genetic cause is present which often results in therapy-resistant obesity. Liraglutide is a glucagon-like peptide-1 (GLP-1) analogue, which has beneficial effects on satiety and weight in common obesity. We present the effects of GLP-1 analogues in adults with a molecularly proven genetic cause of their overweight or obesity. All patients were treated with liraglutide 3.0 mg daily, in addition to intensive supportive lifestyle treatment. Anthropometrics, metabolic parameters, resting energy expenditure (REE), side effects, and subjectively reported satiety and quality of life were assessed. Two patients with 16p11.2 deletion syndrome and two patients with heterozygous pathogenic melanocortin-4 receptor variants were treated. At baseline, their age ranged between 21 and 32 years and body mass index (BMI) ranged between 28.1 and 55.7 kg/m² . At follow-up (ranges 43 weeks-12 years), a mean change in BMI and waist circumference was observed of -5.7 ± 3.8 kg/m² and -15.2 ± 21.1 cm, respectively. All patients achieved ≥5% weight loss, three of them lost ≥10% of their body weight. All patients reported improved quality of life and three of them reported ameliorated satiety. Moreover, improvement of glycaemic control and dyslipidaemia were seen. In two patients, REE before and during treatment was measured, which either increased (+26% of predicted REE) or decreased (-18% of predicted REE). Two patients experienced mild side effects for a brief period. In conclusion, our case series shows beneficial effects of GLP-1 analogues on weight, metabolic parameters and quality of life in all four patients with genetic obesity.

The Diagnostic Journey of a Patient with Prader-Willi-Like Syndrome and a Unique Homozygous SNURF-SNRPN Variant; Bio-Molecular Analysis and Review of the Literature

Prader–Willi syndrome (PWS) is a rare genetic condition characterized by hypotonia, intellectual disability, and hypothalamic dysfunction, causing pituitary hormone deficiencies and hyperphagia, ultimately leading to obesity. PWS is most often caused by the loss of expression of a cluster of genes on chromosome 15q11.2-13. Patients with Prader–Willi-like syndrome (PWLS) display features of the PWS phenotype without a classical PWS genetic defect. We describe a 46-year-old patient with PWLS, including hypotonia, intellectual disability, hyperphagia, and pituitary hormone deficiencies. Routine genetic tests for PWS were normal, but a homozygous missense variant NM_003097.3(SNRPN):c.193C>T, p.(Arg65Trp) was identified. Single nucleotide polymorphism array showed several large regions of homozygosity, caused by high-grade consanguinity between the parents. Our functional analysis, the ‘Pipeline for Rapid in silico, in vivo, in vitro Screening of Mutations’ (PRiSM) screen, showed that overexpression of SNRPN-p.Arg65Trp had a dominant negative effect, strongly suggesting pathogenicity. However, it could not be confirmed that the variant was responsible for the phenotype of the patient. In conclusion, we present a unique homozygous missense variant in SNURF-SNRPN in a patient with PWLS. We describe the diagnostic trajectory of this patient and the possible contributors to her phenotype in light of the current literature on the genotype–phenotype relationship in PWS.

Dextroamphetamine Treatment for Children With Hypothalamic Obesity

Introduction: Hypothalamic obesity (HO) in children can be either genetic or acquired, as a result of a suprasellar tumor or its treatment. HO, resulting from hyperphagia and/or a decreased resting energy expenditure (REE), may have devastating consequences for the child and its family. Currently, no effective drug treatment is yet available for HO. Amphetamines – commonly used in children with attention-deficit/hyperactivity disorder – are known for their stimulant effect on REE and inhibitory effect on appetite. We here present our experiences of dextroamphetamine treatment in children and adolescents with acquired or genetic HO. Methods: A retrospective cohort evaluation was performed of patients (n = 18) treated with dextroamphetamine at 2 endocrine pediatric clinics. Off-label use of dextroamphetamine was initiated in patients with progressive therapy resistant acquired HO (n = 13) and in patients with genetic obesity (n = 5). Initial treatment dosing was once or twice daily 5mg. This dose was weekly increased with 5 mg/day depending on the patient’ wellbeing and the presence of side effects, to a maximum of 0.5 mg/kg/day. Anthropometrics and REE at start and during follow-up, changes in (hyperphagic) behavior, and side effects were assessed.

Results: At start of treatment, mean age was 12.8 years ± 3.4 [range 7.1–17.9] and mean REE was 69.5%± 18.5 (n = 15). At follow-up, mean treatment duration was 18.3 months ± 14.7. Ten out of eighteen children (55.6%) showed clinically relevant weight loss. In 10/13 patients with acquired HO, weight loss was observed (mean ΔBMI SDS -1.09 ± 1.00), in one patient BMI stabilization (ΔBMI SDS +0.03), and in two patients an increase in BMI SDS was seen (mean ΔBMI SDS +0.32 ± 0.05). Of nine children with acquired HO and measurement of REE before and during treatment, a mean REE increase of +15.3% ± 10.5 was observed. In three out of five patients with genetic obesity, initially weight loss was observed resulting in BMI stabilization at end of follow-up due to weight regain (mean ΔBMI SDS -0.08 ± 0.19). In these patients, no difference in REE before and during treatment was observed. In two patients an increase in BMI SDS was seen (mean ΔBMI SDS +0.29 ± 0.25). However, one patient discontinued treatment after one month, due to hypertension. Thirteen out of 18 children (72.2%) reported improvement of either their hyperphagia, energy level, and/or behavior. No serious side effects were reported.

Conclusion: In children and adolescents with acquired HO, treatment with dextroamphetamine may significantly lower BMI, reduce hyperphagia and improve activity level. In genetic HO, these effects were less pronounced. Future studies in a larger cohort and with randomized controlled designs are needed to support these results.

Effects of Glucagon-Like-Peptide-1 Analogue Treatment in Genetic Obesity

Introduction: Obesity is highly prevalent, comes with serious health burden and is difficult to treat. In a minority, there is a genetic cause for the obesity. In these patients, therapy-resistant obesity is often observed despite intensive lifestyle treatment. Moreover, it is still unclear whether bariatric surgery is less successful in genetic obesity. Liraglutide is a Glucagon-Like-Peptide-1 (GLP-1) receptor agonist or GLP-1 analogue, showing positive effects on metabolic parameters, satiety and weight loss in lifestyle-induced obesity. We present our experiences of GLP-1 analogue treatment in patients with genetic obesity disorders. Methods: Adults with overweight or severe obesity and a molecularly proven genetic cause were treated with liraglutide 3,0 mg daily, in addition to ongoing intensive supportive lifestyle treatment. Anthropometrics, metabolic parameters, resting energy expenditure (REE), side effects, and subjectively reported satiety and quality of life were assessed. Results: Two patients with a heterozygous pathogenic melanocortin 4 recepter variant and two patients with 16p11.2 deletion syndrome, ranging in age between 21 and 32 years and in BMI between 28.1 and 55.7 kg/m² at baseline, were treated. At end of follow-up, ranging between 33 weeks and 12 years, a mean change in BMI and waist circumference was observed of -5.7 ± 3.8 kg/m² and -15.2 ± 21.1 cm, respectively. All patients reported better quality of life, three of them also reported improved satiety. Moreover, improvement of metabolic parameters was seen. No clear effect on REE was observed. Two patients experienced mild side effects, e.g. nausea and stomach pain, for a brief period.

Conclusion: We here show beneficial effects of GLP-1 analogues on weight, metabolic parameters, and quality of life in four patients with genetic obesity. Satiety improved in three of the four patients. All patient achieved at least the clinically relevant 5–10% weight loss. Our findings suggest that GLP-1 analogue treatment might be an effective treatment option, in addition to a healthy lifestyle, for patients with genetic obesity.

Bariatric Surgery for Monogenic Non-syndromic and Syndromic Obesity Disorders

PURPOSE OF REVIEW

The global prevalence of obesity has increased rapidly over the last decades, posing a severe threat to human health. Currently, bariatric surgery is the most effective therapy for patients with morbid obesity. It is unknown whether this treatment is also suitable for patients with obesity due to a confirmed genetic defect (genetic obesity disorders). Therefore, this review aims to elucidate the role of bariatric surgery in the treatment of genetic obesity.

RECENT FINDINGS

In monogenic non-syndromic obesity, an underlying genetic defect seems to be the most important factor determining the efficacy of bariatric surgery. In syndromic obesity, bariatric surgery result data are scarce, and even though some promising follow-up results have been reported, caution is required as patients with more severe behavioral and developmental disorders might have poorer outcomes. There is limited evidence in support of bariatric surgery as a treatment option for genetic obesity disorders; hence, no strong statements can be made regarding the efficacy and safety of these procedures for these patients. However, considering that patients with genetic obesity often present with life-threatening obesity-related comorbidities, we believe that bariatric surgery could be considered a last-resort treatment option in selected patients.

Identifying underlying medical causes of pediatric obesity: Results of a systematic diagnostic approach in a pediatric obesity center

Background

Underlying medical causes of obesity (endocrine disorders, genetic obesity disorders, cerebral or medication-induced obesities) are thought to be rare. Even in specialized pediatric endocrinology clinics, low diagnostic yield is reported, but evidence is limited. Identifying these causes is vital for patient-tailored treatment.

Objectives

To present the results of a systematic diagnostic workup in children and adolescents referred to a specialized pediatric obesity center.

Methods

This is a prospective observational study. Prevalence of underlying medical causes was determined after a multidisciplinary, systematic diagnostic workup including growth charts analysis, extensive biochemical and hormonal assessment and genetic testing in all patients.

Results

The diagnostic workup was completed in n = 282 patients. Median age was 10.8 years (IQR 7.7–14.1); median BMI +3.7SDS (IQR +3.3-+4.3). In 54 (19%) patients, a singular underlying medical cause was identified: in 37 patients genetic obesity, in 8 patients cerebral and in 9 patients medication-induced obesities. In total, thirteen different genetic obesity disorders were diagnosed. Obesity onset <5 years (p = 0.04) and hyperphagia (p = 0.001) were indicators of underlying genetic causes, but only in patients without intellectual disability (ID). Patients with genetic obesity with ID more often had a history of neonatal feeding problems (p = 0.003) and short stature (p = 0.005). BMI-SDS was not higher in patients with genetic obesity disorders (p = 0.52). Patients with cerebral and medication-induced obesities had lower height-SDS than the rest of the cohort.

Conclusions

To our knowledge, this is the first study to report the results of a systematic diagnostic workup aimed at identifying endocrine, genetic, cerebral or medication-induced causes of pediatric obesity. We found that a variety of singular underlying causes were identified in 19% of the patients with severe childhood obesity. Because of this heterogeneity, an extensive diagnostic approach is needed to establish the underlying medical causes and to facilitate disease-specific, patient-tailored treatment.

Functional Analysis of the SIM1 Variant p.G715V in 2 Patients With Obesity

CONTEXT

Single-minded homologue 1 (SIM1) is a transcription factor with several physiological and developmental functions. Haploinsufficiency of SIM1 is associated with early-onset obesity with or without Prader-Willi-like (PWL) features and may exhibit incomplete penetrance.

CASE DESCRIPTION

Next-generation sequencing was performed for 2 male patients with obesity, including 1 man presenting with intellectual disability (ID), body mass index (BMI) of 47.4, and impulse-control disorder, and the other man with early obesity (BMI of 36); sequencing revealed a missense variant in SIM1 (c.2144G>T; p.G715V) in both individuals. Previous studies have identified several disease-associated variants that fall near the p.G715V variant within the C-terminal domain of SIM1. We examined p.G715V variant stability and activity in a doxycycline-inducible stable cell line transfected with an artificial reporter construct and either ARNT or ARNT2 as a partner protein.

CONCLUSIONS

Functional testing of the p.G715V variant revealed a significant reduction in SIM1-mediated transcriptional activity. We also generated the first ab initio hybrid protein model for full-length SIM1 to show the predicted spatial relationship between p.G715V and other previously described variants in this region and identified a putative mutation hotspot within the C-terminus. Significant clinical heterogeneity has been observed in patients with SIM1 variants, particularly with regards to the PWL phenotype. In the patient with ID, a second variant of uncertain significance in CHD2 was identified that may contribute to his ID and behavioral disturbances, emphasizing the role of additional genetic modifiers.

Leptin receptor deficiency: a systematic literature review and prevalence estimation based on population genetics

OBJECTIVE

Leptin receptor (LepR) deficiency is an autosomal-recessive endocrine disorder causing early-onset severe obesity, hyperphagia and pituitary hormone deficiencies. As effective pharmacological treatment has recently been developed, diagnosing LepR deficiency is urgent. However, recognition is challenging and prevalence is unknown. We aim to elucidate the clinical spectrum and to estimate the prevalence of LepR deficiency in Europe.

DESIGN

Comprehensive epidemiologic analysis and systematic literature review.

METHODS

We curated a list of LEPR variants described in patients and elaborately evaluated their phenotypes. Subsequently, we extracted allele frequencies from the Genome Aggregation Database (gnomAD), consisting of sequencing data of 77 165 European individuals. We then calculated the number of individuals with biallelic disease-causing LEPR variants.

RESULTS

Worldwide, 86 patients with LepR deficiency are published. We add two new patients, bringing the total of published patients to 88, of which 21 are European. All patients had early-onset obesity; 96% had hyperphagia; 34% had one or more pituitary hormone deficiencies. Our calculation results in 998 predicted patients in Europe, corresponding to a prevalence of 1.34 per 1 million people (95% CI: 0.95-1.72).

CONCLUSIONS

This study shows that LepR deficiency is more prevalent in Europe (n = 998 predicted patients) than currently known (n = 21 patients), suggesting that LepR deficiency is underdiagnosed. An important cause for this could be lack of access to genetic testing. Another possible explanation is insufficient recognition, as only one-third of patients has pituitary hormone deficiencies. With novel highly effective treatment emerging, diagnosing LepR deficiency is more important than ever.

A comprehensive diagnostic approach to detect underlying causes of obesity in adults

Obesity is a worldwide growing problem. When confronted with obesity, many health care providers focus on direct treatment of the consequences of adiposity. We plead for adequate diagnostics first, followed by an individualized treatment. We provide experience-based and evidence-based practical recommendations (illustrated by clinical examples), to detect potential underlying diseases and contributing factors. Adult patients consulting a doctor for weight gain or obesity should first be clinically assessed for underlying diseases, such as monogenetic or syndromic obesity, hypothyroidism, (cyclic) Cushing syndrome, polycystic ovarian syndrome (PCOS), hypogonadism, growth hormone deficiency, and hypothalamic obesity. The most important alarm symptoms for genetic obesity are early onset obesity, dysmorphic features/congenital malformations with or without intellectual deficit, behavioral problems, hyperphagia, and/or striking family history. Importantly, also common contributing factors to weight gain should be investigated, including medication (mainly psychiatric drugs, (local) corticosteroids, insulin, and specific β-adrenergic receptor blockers), sleeping habits and quality, crash diets and yoyo-effect, smoking cessation, and alcoholism. Other associated conditions include mental factors such as chronic stress or binge-eating disorder and depression.Identifying and optimizing the underlying diseases, contributing factors, and other associated conditions may not only result in more effective and personalized treatment but could also reduce the social stigma for patients with obesity.

Genetic analysis in the bariatric clinic; impact of a PTEN gene mutation

Background

Pathogenic PTEN gene mutations are known to cause PTEN tumor hamartoma syndrome. Recent studies also suggest a role for PTEN mutations in the pathogenesis of obesity. No PTEN mutations have been reported among bariatric surgery patients and obesity treatment results are unknown. Since preventive screening for associated tumors is offered to patients with molecular proven PTEN hamartoma tumor syndrome, recognition of this condition in the bariatric surgery clinic is important.

Method

We present a patient with morbid obesity who carries a known pathogenic PTEN mutation, identified at the bariatric surgery clinic using an obesity gene panel consisting of 52 obesity–associated genes. We analyzed the weight loss response during the first 3 years after Sleeve Gastrectomy.

Results

At 1, 2 and 3 years after surgery, the patient achieved a Total Body Weight Loss of 39.4%, 48.8% and 44.9%, respectively. This corresponds to the results of a control group of 18 female patients with normal genetic test results.

Conclusion

Our patient illustrates the importance of recognizing this serious genetic condition for which preventive cancer screening options are available. The positive weight loss results after Sleeve Gastrectomy suggest that this could be a successful treatment option for obesity patients with PTEN mutations.

[A girl with 16p11.2 deletion syndrome]

16p11.2 deletion syndrome is one of the most prevalent microdeletion syndromes in the world. Nevertheless, many doctors are not (yet) familiar with this syndrome. Prevalence has been estimated at approximately 3 in 10,000. The deletion can be identified in around 1 out of 100 people with autism. The syndrome is characterized by a wide range of phenotypic features including developmental delay, autism, obesity, increased head circumference, and epilepsy. Here we describe an 8-year-old female patient with developmental delay, autistic features and hyperphagia. After diagnosis of 16p11.2 deletion syndrome, her parents struggled due to limited information and support provision by healthcare staff. Since then, multidisciplinary healthcare has been introduced for this condition. In parallel, the patient's parents started an online support group for Dutch patients and parents. Given the diverse phenotype of 16p11.2 deletion syndrome, multidisciplinary collaboration is important. Establishing the diagnosis contributes to better treatment and understanding for parents and healthcare providers.

The pathogenesis of obesity

Body fat mass increases when energy intake exceeds energy expenditure. In the long term, a positive energy balance will result in obesity. The worldwide prevalence of obesity has increased dramatically, posing a serious threat to human health. Therefore, insight in the pathogenesis of obesity is important to identify novel prevention and treatment strategies. This review describes the physiology of energy expenditure and energy intake in the context of body weight gain in humans. We focus on the components of energy expenditure and the regulation of energy intake. Finally, we describe rare monogenetic causes leading to an impairment in central regulation of food intake and obesity.

Genetics of Obesity

Obesity is caused by an imbalance between energy intake and output, influenced by numerous environmental, biological, and genetic factors. Only a minority of people with obesity have a genetic defect that is the main cause of their obesity. A key symptom for most of these disorders is early-onset obesity and hyperphagia. For some genetic obesity disorders, the hyperphagia is the main characteristic, often caused by disruptions of the leptin-melanocortin pathway, the central pathway that regulates the body's satiety and energy balance. For other disorders, obesity is part of a distinct combination of other clinical features such as intellectual disability, dysmorphic facial features, or organ abnormalities. This chapter focuses on genetic obesity disorders and also summarizes the present knowledge on the genetics of the more common polygenic/multifactorial obesity.

Extensive Phenotyping for Potential Weight-Inducing Factors in an Outpatient Population with Obesity

BACKGROUND

Obesity has been associated with miscellaneous weight-inducing determinants. A comprehensive assessment of known obesity-related factors other than diet and physical activity within one cohort is currently lacking.

OBJECTIVES

To assess the prevalence of potential contributors to obesity and self-reported triggers for marked weight gain in an adult population with obesity and between obesity classes.

METHODS

In this observational cohort study, we assessed 408 persons with obesity (aged 41.3 ± 14.2 years, BMI 40.5 ± 6.2) visiting our obesity clinic. They were evaluated for use of weight-inducing drugs, hormonal abnormalities, menarcheal age, (high) birth weight, sleep deprivation, and obstructive sleep apnea syndrome (OSAS). We additionally assessed self-reported triggers for marked weight gain and performed genetic testing in patients suspected of genetic obesity.

RESULTS

Nearly half of the patients were using a potentially weight-inducing drug, which was also the most reported trigger for marked weight gain. For the assessed hormonal conditions, a relatively high prevalence was found for hypothyroidism (14.1%), polycystic ovary syndrome (12.0%), and male hypogonadism (41.7%). A relatively low average menarcheal age (12.6 ± 1.8 years) was reported, whereas there was a high prevalence of a high birth weight (19.5%). Sleep deprivation and OSAS were reported in, respectively, 14.5 and 13.7% of the examined patients. Obesity class appeared to have no influence on the majority of the assessed factors. Of the genetically analyzed patients, a definitive genetic diagnosis was made in 3 patients (1.9%).

CONCLUSIONS

A thorough evaluation of patients with obesity yields a relatively high prevalence of various potentially weight-inducing factors. Diagnostic screening of patients with obesity could therefore benefit these patients by potentially reducing the social stigma and improving the outcomes of obesity treatment programs by tackling, where possible, the weight-inducing factors in advance.

The role of obesity in the fatal outcome of Schaaf-Yang syndrome: Early onset morbid obesity in a patient with a MAGEL2 mutation

Schaaf-Yang syndrome (SYS) was recently identified as a genetic condition resembling Prader-Willi syndrome. It is caused by mutations on the paternal allele of the MAGEL2 gene, a gene that has been mapped in the Prader-Willi critical region. Here, we present an infant with SYS who sadly died because of the combination of hypotonia, sleep apnea, and obesity. A heterozygous premature stop mutation in MAGEL2 was identified in the patient. The main factors reported in the mortality of SYS are lethal arthrogryposis multiplex congenita, fetal akinesia, and pulmonary problems. Our clinical report indicates that obesity and its complications are an important additional factor in the mortality associated with SYS. Therefore, we advise to strictly monitor weight and intensively treat overweight and obesity in SYS.

Genetic obesity: next-generation sequencing results of 1230 patients with obesity

BACKGROUND

Obesity is a global and severe health problem. Due to genetic heterogeneity, the identification of genetic defects in patients with obesity can be time consuming and costly. Therefore, we developed a custom diagnostic targeted next-generation sequencing (NGS)-based analysis to simultaneously identify mutations in 52 obesity-related genes. The aim of this study was to assess the diagnostic yield of this approach in patients with suspected genetic obesity.

METHODS

DNA of 1230 patients with obesity (median BMI adults 43.6 kg/m²; median body mass index-SD children +3.4 SD) was analysed in the genome diagnostics section of the Department of Genetics of the UMC Utrecht (The Netherlands) by targeted analysis of 52 obesity-related genes.

RESULTS

In 48 patients pathogenic mutations confirming the clinical diagnosis were detected. The majority of these were observed in the MC4R gene (18/48). In an additional 67 patients a probable pathogenic mutation was identified, necessitating further analysis to confirm the clinical relevance.

CONCLUSIONS

NGS-based gene panel analysis in patients with obesity led to a definitive diagnosis of a genetic obesity disorder in 3.9% of obese probands, and a possible diagnosis in an additional 5.4% of obese probands. The highest yield was achieved in a selected paediatric subgroup, establishing a definitive diagnosis in 12 out of 164 children with severe early onset obesity (7.3%). These findings give a realistic insight in the diagnostic yield of genetic testing for patients with obesity and could help these patients to receive (future) personalised treatment.

Young girl with severe early-onset obesity and hyperphagia

This case report of an infant with severe early-onset obesity illustrates the societal condemnation of persons with obesity. In addition, it underlines the importance of diagnosing rare forms of monogenic obesity, even if no drug treatment is available. Here, we describe a 2-year-old girl with severe progressive obesity from birth onwards due to insatiable hunger. Genetic studies eventually reveal that the girl has a monogenic form of obesity caused by two mutations in the LEPR gene. No drug treatment is available (as yet) for this disease. Parents describe the stigmatic remarks they have to deal with every day. Diagnosing this rare genetic disorder was very important for understanding that satiety regulation is a complex system, of which willpower is only a small portion. In these patients, reduction of obesity can be achieved, but a different approach to lifestyle intervention is needed.

[Genetic obesity: new diagnostic options]

- Obesity is an important risk factor for morbidity and premature death, as well as a contributing factor to psychosocial problems. The incidence of obesity has increased dramatically over the last few decades.- Obesity is considered to be a multifactorial condition in which both environmental factors and genetic factors play a part.- In approximately 5% of patients with morbid obesity, a monogenic cause can be identified. Mutations in the MC4R gene are the most frequently occurring monogenic cause of obesity.- The department of Genetics at the VU University Medical Center Amsterdam offers morbidly obese patients a diagnostic analysis of 50 obesity-associated genes. - An underlying obesity-associated genetic defect can influence patient response to certain treatments. Therefore, if the gene defect is known, it can be taken into account when considering treatment options.- The understanding of the genetics of obesity will significantly contribute to research into the development of personalized treatment options.