• Vidhu V Thaker, Kristyn M Esteves, Meghan C Towne, Catherine A Brownstein, Philip M James, Laura Crowley, Joel N Hirschhorn, Sarah H Elsea, Alan H Beggs, Jonathan Picker, and Pankaj B Agrawal.
• Division of Endocrinology (V.V.T., J.N.H.), Newborn Medicine (K.M.E., P.B.A.), and Genetics and Genomics (M.C.T., C.A.B., L.C., A.H.B., J.P., P.B.A.), Department of Medicine, and Gene Discovery Core (M.C.T., C.A.B., L.C., A.H.B., J.P., P.B.A.), The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115; Genetics and Metabolism (P.M.J.), Phoenix Children's Hospital, Phoenix, Arizona 85006; and Department of Molecular and Human Genetics (S.H.E.), Baylor College of Medicine, Houston, Texas 77030.
• J. Clin. Endocrinol. Metab. 2015 May 1; 100 (5): 1723-30.

ContextThe current obesity epidemic is attributed to complex interactions between genetic and environmental factors. However, a limited number of cases, especially those with early-onset severe obesity, are linked to single gene defects. Rapid-onset obesity with hypothalamic dysfunction, hypoventilation and autonomic dysregulation (ROHHAD) is one of the syndromes that presents with abrupt-onset extreme weight gain with an unknown genetic basis.ObjectiveTo identify the underlying genetic etiology in a child with morbid early-onset obesity, hypoventilation, and autonomic and behavioral disturbances who was clinically diagnosed with ROHHAD syndrome. Design/Setting/Intervention: The index patient was evaluated at an academic medical center. Whole-exome sequencing was performed on the proband and his parents. Genetic variants were validated by Sanger sequencing.ResultsWe identified a novel de novo nonsense mutation, c.3265 C>T (p.R1089X), in the retinoic acid-induced 1 (RAI1) gene in the proband. Mutations in the RAI1 gene are known to cause Smith-Magenis syndrome (SMS). On further evaluation, his clinical features were not typical of either SMS or ROHHAD syndrome.ConclusionsThis study identifies a de novo RAI1 mutation in a child with morbid obesity and a clinical diagnosis of ROHHAD syndrome. Although extreme early-onset obesity, autonomic disturbances, and hypoventilation are present in ROHHAD, several of the clinical findings are consistent with SMS. This case highlights the challenges in the diagnosis of ROHHAD syndrome and its potential overlap with SMS. We also propose RAI1 as a candidate gene for children with morbid obesity.

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