New Thoughts on Pediatric Genetic Obesity: Pathogenesis, Clinical Characteristics and Treatment Approach

Historically, some genetic syndromes and monogenic forms of obesity have been identified by clinical features and by sequencing candidate genes in patients with severe obesity. The phenotypic expression of genetic factors involved in obesity is variable, thereby allowing to distinguish several clinical pictures of obesity. Monogenic obesity is described as rare and severe early‐onset obesity with abnormal feeding behavior and endocrine disorders. Many of the findings emerged from studying families who displayed a classical Mendelian pattern of inheritance. On the contrary, patients with syndromic obesity show a various degree of intellectual disability, different dysmorphic features, and organ‐specific abnormalities. But to date, not all involved genes have been identified so far. New diagnostic tools, such as genome‐wide studies, array CGH, and whole‐exome sequencing, have highlighted more complex models of inheritance, and even more candidate genes were identified. This increase of knowledge may provide insights into the mechanisms involved in the regulation of body weight and finally lead to specific treatments. In these patients, hyperphagia is often a primary phenotypic component. Substantial gaps in understanding the molecular basis of inherited hyperphagia syndromes are present today with a lack of mechanistic targets that can serve as a basis for pharmacologic and behavioral treatments. We have evaluated retrospectively the literature data on weight, body mass index (BMI), clinical features, treatments, and treatment response in pediatric patients with forms of genetic obesity. However, this chapter provides an updated picture of emerging knowledge outlined by the more comprehensive genetic approaches, trying to outline more candidate genes for these forms of genetic obesity. Relevant papers will be identified through systematic searches of the PubMed, EMBASE and Cochrane databases. All published studies in the English language concerning these disorders will be evaluated. Keywords in the literature search will be entered in all combinations. Searches will be augmented by manually reviewing the reference lists of all original articles and all systematic review articles, with each study being evaluated for inclusion.