👤 Chrisitne Poitou

Pathogenic variants in five established leptin-melanocortin pathway genes (LEP, LEPR, MC4R, PCSK1, POMC) are associated with severe early-onset obesity and are targets for emerging treatments. However, these variants are rare in these patients, suggesting the involvement of additional genes interacting with this pathway. Next-generation sequencing (NGS) analysis was performed in 395 patients with severe obesity, including 213 children (mean BMI: 56.3 kg/m Pathogenic heterozygous variants were identified in 34 patients (8.6%), 18 of them harboring pathogenic variants in the 15 additional genes. In adults, early-onset obesity was more frequent in potentially pathogenic variants carriers than in non-carriers (83.3% vs. 55.0%, p = 0.04). No differences were observed in the other phenotypic characteristics. This supports the relevance of expanded genetic testing in severe obesity. Early-onset obesity remains a key clinical feature to guide genetic investigation and identify patients who may benefit from early personalized care and targeted treatments. Show less

Genetic forms of obesity, including monogenic (MO) and syndromic (SO) obesity, are characterised by severe, early-onset weight gain due to disrupted central regulation of body weight, typically involving key pathways such as the leptin-melanocortin axis. These alterations result in marked hyperphagia and complex eating behaviours, yet clinical characterisation remains limited. This review aimed to describe the multidimensional eating behaviour profiles across genetically confirmed obesity, explore their variability, and evaluate existing assessment tools to support early diagnosis, personalised care, and therapeutic monitoring. We conducted a systematic review following PRISMA guidelines including publications up to 4 September 2025. A total of 162 studies involving individuals with genetically confirmed SO or MO were analysed. Eating behaviours were categorised into nine dimensions: food-centred thinking, food-seeking/stealing, hunger/satiety, ingestive/oral behaviours, nutritional quality, food preferences, food acceptability, loss of control eating, and eating restraint. Assessment tools and methodologies were systematically reviewed. Hyperphagia was consistently reported across genetic aetiologies, though definitions and measures remain heterogeneous. Prader-Willi syndrome (PWS), the most studied condition, was associated with early-onset hyperphagia, increased hunger, pronounced food preoccupation, compulsive food-seeking/stealing and strong preferences for carbohydrate-rich, large quantities and unusual food items. Similar behavioural traits were found in other SO and MO, including Bardet-Biedl syndrome, Alström syndrome, Fragile X syndrome, WAGR syndrome, pseudohypoparathyroidism Ia, 16p11.2 deletion and LEPR, POMC, and MC4R deficiencies. Behavioural traits appeared relatively consistent across sex, age, and genotypes within syndromes. Most studies relied on caregiver reports; existing tools such as the Hyperphagia Questionnaire (HQ) and Food-Related Problem Questionnaire (FRPQ), developed primarily for PWS, did not fully capture the behavioural spectrum or suit all cognitive profiles. Tools applicable to individuals without intellectual developmental disorders, particularly adults living independently, remain scarce. This is the first systematic review to comprehensively map eating behaviours across rare genetic obesity using a multidimensional approach. It highlights the shared feature of disrupted appetite regulation and emphasises the need for standardised, multidimensional tools suitable for both clinical and research contexts. Better behavioural characterisation will support targeted therapies and improve outcome monitoring in these high-need populations. Show less

A total of 150 clinicians and researchers representing 19 countries came together in person and online to participate in the highly anticipated 2nd International Meeting on Pathway-Related Obesity: Vision & Evidence (IMPROVE), held on 13-15 December 2023 in Paris, France. Building on the success of the inaugural event in 2022, this gathering served as a pivotal platform for attendees to delve into the latest scientific and clinical developments in hyperphagia and early-onset obesity caused by rare melanocortin-4 receptor (MC4R) pathway disease. The central objective of the meeting was to explore the complexities of MC4R pathway-related diseases and generate opportunities for collaborative dialogue among delegates for the advancement of this field. The event unfolded across three distinct sessions, with a dedicated focus on monogenic MC4R pathway disease, Bardet-Biedl syndrome (BBS) and hypothalamic obesity, together with a discussion on the future of the field. Additionally, the agenda featured three insightful workshops designed to facilitate in-depth discussions. One workshop focused on the genetics of monogenic MC4R pathway diseases, another scrutinised the genetics of BBS and the final workshop examined patient management through the exploration of clinical cases. As we reflect on the wealth of information disseminated and the collaborative spirit that permeated the meeting, it becomes clear that IMPROVE 2023 was not merely an assembly of professionals; it was a forum where the future of research in rare MC4R pathway diseases and patient care took centre stage. Here, we encapsulate the key insights, discussions, and initiatives that emerged from this important meeting. Show less

Biallelic variants in the pro-opiomelanocortin gene (POMC) can cause hypocortisolism, hypopigmentation, and early-onset obesity. Following the identification of 2 patients of combined pituitary hormone deficiency (CPHD), we investigated the prevalence of this association among carriers of rare pathogenic or likely pathogenic (P/LP) POMC variants. This study is a case report and systematic literature review. Genetic analysis was conducted in a family with 2 cousins with childhood-onset obesity and CPHD. We assessed CPHD in carriers for biallelic pathogenic POMC variants using data from the literature and Human Gene Mutation Database. Clinical and biological data were collected, including pituitary axis involvement, obesity onset age, and pituitary imaging results. The 2 cousins, compound heterozygous for POMC variants, developed CPHD following initial hypocortisolism, with subsequent hypothyroidism, growth hormone deficiency, and hypogonadism. Among 41 patients with biallelic POMC variants identified in the literature, 20 had rare homozygous/compound heterozygous P/LP POMC variants and detailed endocrine evaluations. Of these, 40% presented with CPHD, always associated with early-onset severe obesity and hypocortisolism. Growth hormone deficiency was the most frequent (75%), followed by thyrotropic and gonadotropic deficiencies (62.5%). No anomalies were revealed in pituitary imaging. Two patients recovered the gonadotropic axis after treatment with the MC4R agonist. These findings underscore the potential for CPHD to occur in carriers of biallelic pathogenic POMC variants. Sequencing the full POMC, including coding and regulatory regions, is crucial in CPHD cases, alongside evaluating all pituitary axes in neonatal hypocortisolism. Beyond weight regulation, setmelanotide may modulate hypothalamic-pituitary function, with implications for fertility. Show less

Monogenic defects in the leptin-melanocortin pathway are associated with hyperphagia and severe, early-onset obesity. Early childhood growth patterns in height, weight, and BMI, might serve as phenotypic markers for specific genetic disorders; however, reliable data are scarce. This study aimed to evaluate the natural history of height, weight, and BMI in early childhood in a large European group of individuals with monogenic obesity. This multicentre observational study analysed height, weight, and BMI from birth to age 5 years in individuals diagnosed with biallelic (likely) pathogenic LEP, LEPR, POMC, PCSK1, or MC4R variants or monoallelic (likely) pathogenic MC4R variants from six European centres (Berlin and Ulm, Germany; Cambridge, UK; Madrid, Spain; Paris, France; Rotterdam, Netherlands). All patient data up to May 31, 2022 were included in this analysis. All individuals had at least two height or weight measurements between birth and age 5 years. Early childhood growth trajectories were compared with those of control children with obesity without a known genetic cause, following a negative next-generation sequencing panel. Diagnostic performance of BMI as a predictor test for monogenic obesity was also evaluated. We included 147 individuals with monogenic obesity. From the age of 6 months onwards, children with biallelic variants (n=88, 55% female vs 45% male) had substantially higher BMIs than those with monoallelic MC4R variants (n=59, 53% female vs 47% male) and control children (n=113, 59% female vs 41% male). Children with biallelic LEP, LEPR, and MC4R variants showed a steep BMI increase during the first year of life, followed by a plateau until age 5 years, whereas those with biallelic POMC variants did not plateau. Accelerated linear growth was only observed in children with biallelic MC4R variants starting from age 1 year. The optimal BMI cut-off for distinguishing individuals with biallelic variants from control individuals was identified at age 2 years, with a test positivity cutoff of 24·0 kg/m This study identified characteristic early childhood BMI trajectories for different forms of monogenic obesity. From age 6 months onwards, individuals with biallelic variants can be distinguished from those with monoallelic variants and common obesity. A BMI ≥24 kg/m Federal Ministry of Education and Research as part of the German Center for Child and Adolescent Health, German Research Foundation, Spanish Ministry of Health, The Wellcome Trust, Botnar Fondation, Leducq Foundation, National Institute for Health Research (NIHR) Cambridge Biomedical Research Centre, and NIHR Senior Investigator Award. Show less

Recessive deficiency of proopiomelanocortin (POMC) causes childhood-onset severe obesity. Cases can now benefit from the melanocortin 4 receptor agonist setmelanotide. Furthermore, a phase 3 clinical trial is evaluating setmelanotide in heterozygotes for POMC. We performed a large-scale genetic analysis to assess the effect of heterozygous, pathogenic POMC variants on obesity. A genetic analysis was performed in a family including 2 cousins with childhood-onset obesity. We analyzed the obesity status of heterozygotes for pathogenic POMC variants in the Human Gene Mutation Database. The association between heterozygous pathogenic POMC variants and obesity risk was assessed using 190,000 exome samples from UK Biobank. The 2 cousins carried a compound heterozygous pathogenic variant in POMC. Six siblings were heterozygotes; only 1 of them had obesity. In Human Gene Mutation Database, we identified 60 heterozygotes for pathogenic POMC variants, of whom 14 had obesity. In UK Biobank, heterozygous pathogenic POMC variants were not associated with obesity risk, but they modestly increased body mass index levels. Heterozygous pathogenic POMC variants do not contribute to monogenic obesity, but they slightly increase body mass index. Setmelanotide use in patients with obesity, which would only be based on the presence of a heterozygous POMC variant, can be questioned. Show less

Impaired cilial signalling in the melanocortin-4 receptor (MC4R) pathway might contribute to obesity in patients with Bardet-Biedl syndrome and Alström syndrome, rare genetic diseases associated with hyperphagia and early-onset severe obesity. We aimed to evaluate the effect of setmelanotide on bodyweight in these patients. This multicentre, randomised, 14-week double-blind, placebo-controlled, phase 3 trial followed by a 52-week open-label period, was performed at 12 sites (hospitals, clinics, and universities) in the USA, Canada, the UK, France, and Spain. Patients aged 6 years or older were included if they had a clinical diagnosis of Bardet-Biedl syndrome or Alström syndrome and obesity (defined as BMI >97th percentile for age and sex for those aged 6-15 years and ≥30 kg/m Between Dec 10, 2018, and Nov 25, 2019, 38 patients were enrolled and randomly assigned to receive setmelanotide (n=19) or placebo (n=19; 16 with Bardet-Biedl syndrome and three with Alström syndrome in each group). In terms of the primary endpoint, 32·3% (95% CI 16·7 to 51·4; p=0·0006) of patients aged 12 years or older with Bardet-Biedl syndrome reached at least a 10% reduction in bodyweight after 52 weeks of setmelanotide. The most commonly reported treatment-emergent adverse events were skin hyperpigmentation (23 [61%] of 38) and injection site erythema (18 [48%]). Two patients had four serious adverse events (blindness, anaphylactic reaction, and suicidal ideation); none were considered related to setmelanotide treatment. Setmelanotide resulted in significant bodyweight reductions in patients with Bardet-Biedl syndrome; however, these results were inconclusive in patients with Alström syndrome. These results support the use of setmelanotide and provided the necessary evidence for approval of this drug as the first treatment for obesity in patients with Bardet-Biedl syndrome. Rhythm Pharmaceuticals. Show less

Pathogenic heterozygous MC4R variants are associated with hyperphagia and variable degrees of obesity. Several research groups have reported short-term weight loss outcomes after bariatric surgery in a few patients with MC4R variants, but lack of longer-term data prevents evidence-based clinical decision-making. Bariatric surgery patients with heterozygous (likely) pathogenic MC4R variants, from three collaborating centers in the Netherlands, France, and the UK, were compared to matched controls (matched 2:1 for age, sex, preoperative BMI, surgical procedure, and diabetes mellitus, but without MC4R mutations). Weight loss and regain outcomes up to 6 years of follow-up were compared. At 60 months of follow-up after RYGB, cases with MC4R variants showed weight regain with a mean of 12.8% (± 10.4 SD) total weight loss (TWL) from nadir, compared to 7.9% (± 10.5 SD) in the controls (p = 0.062). Among patients receiving SG, the cases with MC4R variants experienced inferior weight loss (22.6% TWL) during the first year of follow-up compared to the controls (29.9% TWL) (p = 0.010). This multicenter study reveals inferior mid-term weight outcomes of cases with MC4R variants after SG, compared to RYGB. Since adequate weight loss outcomes were observed after RYGB, this procedure would appear to be an appropriate surgical approach for this group. However, the pattern of weight regain seen in cases with MC4R variants after both RYGB and SG highlights the need for pro-active lifelong management to prevent relapse, as well as careful expectation management. Show less

Gene mutations in the leptin-melanocortin signaling cascade lead to hyperphagia and severe early onset obesity. In most cases, multimodal conservative treatment (increased physical activity, reduced caloric intake) is not successful to stabilize body weight and control hyperphagia. To examine bariatric surgery as a therapeutic option for patients with genetic obesity. Three major academic, specialized medical centers. In 3 clinical centers, we retrospectively analyzed the outcomes of bariatric surgery performed in 8 patients with monogenic forms of obesity with bi-allelic variants in the genes LEPR (n = 5), POMC (n = 2), and MC4R (n = 1). In this group of patients with monogenic obesity, initial bariatric surgery was performed at a median age of 19 years (interquartile range [IQR], 16-23.8 yr). All patients initially experienced weight loss after each bariatric surgery, which was followed by substantial weight regain. In total, bariatric surgery led to a median maximum reduction of body weight of -21.5 kg (IQR, -36.3 to -2.9 kg), median percent excess weight loss (%EWL) of -47.5 %EWL (IQR, -57.6 to -28.9 %EWL). This body weight reduction was followed by median weight regain of 24.1 kg (IQR: 10.0 to 42.0 kg), leading to a final weight change of -24.2 % EWL (IQR: -37.6 to -5.4 %EWL) after a maximum duration of 19 years post surgery. In one patient, bariatric surgery was accompanied by significant complications, including vitamin deficiencies and hernia development. The indication for bariatric surgery in patients with monogenic obesity based on bi-allelic gene mutations and its benefit/risk balance has to be evaluated very cautiously by specialized centers. Furthermore, to avoid an unsuccessful operation, preoperative genetic testing of patients with a history of early onset obesity might be essential, even more since novel pharmacological treatment options are expected. Show less

Gene mutations within the leptin-melanocortin signaling pathway lead to severe early-onset obesity. Recently, a phase 2 trial evaluated new pharmacological treatment options with the MC4R agonist setmelanotide in patients with mutations in the genes encoding proopiomelanocortin (POMC) and leptin receptor (LEPR). During treatment with setmelanotide, changes in skin pigmentation were observed, probably due to off-target effects on the closely related melanocortin 1 receptor (MC1R). Here, we describe in detail the findings of dermatological examinations and measurements of skin pigmentation during this treatment over time and discuss the impact of these changes on patient safety. In an investigator-initiated, phase 2, open-label pilot study, 2 patients with loss-of-function POMC gene mutations and 3 patients with loss-of-function variants in LEPR were treated with the MC4R agonist setmelanotide. Dermatological examination, dermoscopy, whole body photographic documentation, and spectrophotometric measurements were performed at screening visit and approximately every 3 months during the course of the study. We report the results of a maximum treatment duration of 46 months. Skin pigmentation increased in all treated patients, as confirmed by spectrophotometry. During continuous treatment, the current results indicate that elevated tanning intensity levels may stabilize over time. Lips and nevi also darkened. In red-haired study participants, hair color changed to brown after initiation of setmelanotide treatment. Setmelanotide treatment leads to skin tanning and occasionally hair color darkening in both POMC- and LEPR-deficient patients. No malignant skin changes were observed in the patients of this study. However, the results highlight the importance of regular skin examinations before and during MC4R agonist treatment. Show less

The melanocortin 4 receptor (MC4R), a component of the leptin-melanocortin pathway, plays a part in bodyweight regulation. Severe early-onset obesity can be caused by biallelic variants in genes that affect the MC4R pathway. We report the results from trials of the MC4R agonist setmelanotide in individuals with severe obesity due to either pro-opiomelanocortin (POMC) deficiency obesity or leptin receptor (LEPR) deficiency obesity. These single-arm, open-label, multicentre, phase 3 trials were done in ten hospitals across Canada, the USA, Belgium, France, Germany, the Netherlands, and the UK. Participants aged 6 years or older with POMC or LEPR deficiency obesity received open-label setmelanotide for 12 weeks. Participants with at least 5 kg weight loss (or ≥5% if weighing <100 kg at baseline) entered an 8-week placebo-controlled withdrawal sequence (including 4 weeks each of blinded setmelanotide and placebo treatment) followed by 32 additional weeks of open-label treatment. The primary endpoint, which was assessed in participants who received at least one dose of study medication and had a baseline assessment (full analysis set), was the proportion of participants with at least 10% weight loss compared with baseline at approximately 1 year. A key secondary endpoint was mean percentage change in the most hunger score of the 11-point Likert-type scale at approximately 1 year on the therapeutic dose, which was assessed in a subset of participants aged 12 years or older in the full analysis set who demonstrated at least 5 kg weight loss (or ≥5% in paediatric participants if baseline bodyweight was <100 kg) over the 12-week open-label treatment phase and subsequently proceeded into the placebo-controlled withdrawal sequence, regardless of later disposition. These studies are registered with ClinicalTrials.gov, NCT02896192 and NCT03287960. Between Feb 14, 2017, and Sept 7, 2018, ten participants were enrolled in the POMC trial and 11 participants were enrolled in the LEPR trial, and included in the full analysis and safety sets. Eight (80%) participants in the POMC trial and five (45%) participants in the LEPR trial achieved at least 10% weight loss at approximately 1 year. The mean percentage change in the most hunger score was -27·1% (n=7; 90% CI -40·6 to -15·0; p=0·0005) in the POMC trial and -43·7% (n=7; -54·8 to -29·1; p<0·0001) in the LEPR trial. The most common adverse events were injection site reaction and hyperpigmentation, which were reported in all ten participants in the POMC trial; nausea was reported in five participants and vomiting in three participants. In the LEPR trial, the most commonly reported treatment-related adverse events were injection site reaction in all 11 participants, skin disorders in five participants, and nausea in four participants. No serious treatment-related adverse events occurred in both trials. Our results support setmelanotide for the treatment of obesity and hyperphagia caused by POMC or LEPR deficiency. Rhythm Pharmaceuticals. Show less

Monogenic non-syndromic obesity is characterized by severe early-onset obesity with abnormal eating behaviour and endocrine disorders. Genes contributing to these rare forms of obesity are mainly located in the leptin/melanocortin pathway, with typically an autosomal additive inheritance of obesity. The normal function of this hypothalamic pathway is essential for the control of energy balance. Genetic variants are involved in 5-30 % of severe early-onset obesity depending on explored populations. Compared to other genes in the pathway especially leptin (LEP), leptin receptor (LEPR), pro-opiomelanocortin (POMC) and prohormone convertase subtilisin/kexin type 1 (PCSK1), Melanocortin 4 receptor (MC4R)-linked obesity is characterized by obesity of variable severity with no notable endocrine phenotypes. Managing patients with monogenic non-syndromic obesity is clinically challenging since they display complex phenotypes and the obesity is often morbid and refractory to classical treatments. Until recent years, there has been a lack of effective and targeted pharmaceutical molecules except for leptin therapy that was available for leptin deficiency. The picture has changed and new promising molecules acting on the leptin-melanocortin pathway such as setmelanotide -a new MC4R agonist- are now emerging as novel targeted therapeutic opportunities. Show less

Genetic defects underlying the melanocortin-4 receptor (MC4R) signaling pathway lead to severe obesity. Three severely obese LEPR-deficient individuals were administered the MC4R agonist setmelanotide, resulting in substantial and durable reductions in hyperphagia and body weight over an observation period of 45-61 weeks. Compared to formerly developed and tested MC4R agonists, setmelanotide has the unique capability of activating nuclear factor of activated T cell (NFAT) signaling and restoring function of this signaling pathway for selected MC4R variants. Our data demonstrate the potency of setmelanotide in treatment of individuals with diverse MC4R-related pathway deficiencies. Show less