Syndromic obesity with neurodevelopmental delay: Opportunities for targeted interventions

Updates on Rare Genetic Variants, Genetic Testing, and Gene Therapy in Individuals With Obesity

PURPOSE OF REVIEW

The goal of this paper is to aggregate information on monogenic contributions to obesity in the past five years and to provide guidance for genetic testing in clinical care.

RECENT FINDINGS

Advances in sequencing technologies, increasing awareness, access to testing, and new treatments have increased the utilization of genetics in clinical care. There is increasing recognition of the prevalence of rare genetic obesity from variants with mean allele frequency < 5% -new variants in known genes as well as identification of novel genes- causing monogenic obesity. While most of these genes are in the leptin melanocortin pathway, those in adipocytes may also contribute. Common variants may contribute either to higher lifetime tendency for weight gain or provide protection from monogenic obesity. While specific genetic mutations are rare, these segregate in individuals with early-onset severe obesity; thus, collectively genetic etiologies are not as rare. Some genetic conditions are amenable to targeted treatment. Research into the discovery of novel genetic causes as well as targeted treatment is growing over time. The utility of therapeutic strategies based on the genetic risk of obesity is an advancing frontier.

A Comprehensive Review of Syndromic Forms of Obesity: Genetic Etiology, Clinical Features and Molecular Diagnosis

Syndromic obesity refers to obesity occurring with additional clinical findings, such as intellectual disability/developmental delay, dysmorphic features, and congenital malformations. PURPOSE OF REVIEW: To present a narrative review regarding the genetic etiology, clinical description, and molecular diagnosis of syndromic obesity, which is a rare condition with high phenotypic variability and genetic heterogeneity. The following syndromes are presented in this review: Prader-Willi, Bardet-Biedl, Pseudohypoparathyroidism, Alström, Smith-Magenis, Cohen, Temple, 1p36 deletion, 16p11.2 microdeletion, Kleefstra, SIM1-related, Börjeson-Forssman-Lehmann, WAGRO, Carpenter, MORM, and MYT1L-related syndromes. RECENT FINDINGS: There are three main groups of mechanisms for syndromic obesity: imprinting, transcriptional activity regulation, and cellular cilia function. For molecular diagnostic, methods of genome-wide investigation should be prioritized over sequencing of panels of syndromic obesity genes. In addition, we present novel syndromic conditions that need further delineation, but evidences suggest they have a higher frequency of obesity. The etiology of syndromic obesity tends to be linked to disrupted neurodevelopment (central) and is associated with a diversity of genes and biological pathways. In the genetic investigation of individuals with syndromic obesity, the possibility that the etiology of the syndromic condition is independent of obesity should be considered. The accurate genetic diagnosis impacts medical management, treatment, and prognosis, and allows proper genetic counseling.

Biallelic PRMT7 pathogenic variants are associated with a recognizable syndromic neurodevelopmental disorder with short stature, obesity, and craniofacial and digital abnormalities

PURPOSE

Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyzes the methylation of arginine residues on several protein substrates. Biallelic pathogenic PRMT7 variants have previously been associated with a syndromic neurodevelopmental disorder characterized by short stature, brachydactyly, intellectual developmental disability, and seizures. To our knowledge, no comprehensive study describes the detailed clinical characteristics of this syndrome. Thus, we aim to delineate the phenotypic spectrum of PRMT7-related disorder.

METHODS

We assembled a cohort of 51 affected individuals from 39 different families, gathering clinical information from 36 newly described affected individuals and reviewing data of 15 individuals from the literature.

RESULTS

The main clinical characteristics of the PRMT7-related syndrome are short stature, mild to severe developmental delay/intellectual disability, hypotonia, brachydactyly, and distinct facial morphology, including bifrontal narrowing, prominent supraorbital ridges, sparse eyebrows, short nose with full/broad nasal tip, thin upper lip, full and everted lower lip, and a prominent or squared-off jaw. Additional variable findings include seizures, obesity, nonspecific magnetic resonance imaging abnormalities, eye abnormalities (i.e., strabismus or nystagmus), and hearing loss.

CONCLUSION

This study further delineates and expands the molecular, phenotypic spectrum and natural history of PRMT7-related syndrome characterized by a neurodevelopmental disorder with skeletal, growth, and endocrine abnormalities.

Obesity and Overweight Among Children With Medical Complexity

OBJECTIVES

To assess the prevalence of overweight or obesity among children with medical complexity (CMC), compared with children without medical complexity, and explore potentially modifiable mechanisms.

METHODS

This study involved a retrospective cohort of 41 905 children ages 2 to 18 seen in 2019 at a single academic medical center. The primary outcome was overweight or obesity, defined as a body mass index of ≥85% for age and sex. CMC was defined as ≥1 serious chronic condition in ≥1 system. Obesogenic conditions and medications were defined as those typically associated with excess weight gain. Multivariable logistic regression was used to adjust for common confounders.

RESULTS

Of the children in the cohort, 29.5% were CMC. Overweight or obesity prevalence was higher among CMC than non-CMC (31.9% vs 18.4%, P ≤.001, adjusted odds ratio [aOR] 1.27, 95% confidence interval [CI] 1.20-1.35). Among CMC, the risk for overweight or obesity was higher among children with metabolic conditions (aOR 2.09, 95% CI 1.88-2.32), gastrointestinal conditions (aOR 1.23 95% CI 1.06-1.41), malignancies (aOR 1.21 95% CI 1.07-1.38), and Spanish-speaking parents (aOR 1.47 95% CI 1.30-1.67). Among overweight or obese CMC, 91.6% had no obesogenic conditions, and only 8.5% had been seen by a registered dietitian in the previous year.

CONCLUSIONS

CMC are significantly more likely to be overweight or obese when compared with children without medical complexity. Although many CMC cases of overweight appear to be preventable, further research is necessary to determine if and how to prevent comorbid obesity among CMC.