Metabolic Profile of Patients with Smith-Magenis Syndrome: An Observational Study with Literature Review

Background: Smith-Magenis syndrome (SMS) is caused by either interstitial deletions in the 17p11.2 region or pathogenic variants in the RAI1 gene and is marked by a distinct set of physical, developmental, neurological, and behavioral features. Hypercholesterolemia has been described in SMS, and obesity is also commonly found. Aim: To describe and characterize the metabolic phenotype of a cohort of SMS patients with an age range of 2.9-32.4 years and to evaluate any correlations between their body mass index and serum lipids, glycated hemoglobin (HbA1c), and basal insulin levels. Results: Seven/thirty-five patients had high values of both total cholesterol and low-density lipoprotein cholesterol; 3/35 had high values of triglycerides; none of the patients with RAI1 variants presented dyslipidemia. No patients had abnormal fasting glucose levels. Three/thirty-five patients had HbA1c in the prediabetes range. Ten/twenty-two patients with 17p11.2 deletion and 2/3 with RAI1 variants had increased insulin basal levels. Three/twenty-three patients with the 17p11.2 deletion had prediabetes. Conclusion: Our investigation suggests that SMS 'deleted' patients may show a dyslipidemic pattern, while SMS 'mutated' patients are more likely to develop early-onset obesity along with hyperinsulinism.