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N Engl J Med. 2016 Jun 9;374(23):2246-55. doi: 10.1056/NEJMoa1515792. Epub 2016 May 25.

Exome Sequencing and the Management of Neurometabolic Disorders.

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From the Centre for Molecular Medicine and Therapeutics (M.T.-G., C. Shyr, X.C.Y., L.-H.Z., J.J.Y.L., B.I.D., I.G., W.W.W., C.D.K.), the Departments of Medical Genetics (M.T.-G., C. Shyr, C.J.R., X.C.Y., J.J.Y.L., L.A., J.M.F., S.L., M.M., M.I.V.A., A.M.L., W.W.W.), Pediatrics (C.J.R., G.A.H., R.S., L.-H.Z., A.P.B., B.I.D., M.B.C., M.D., T.D., J.D., A. Michoulas, D.M., J.R., K.R.S., K.S., S.E.T., John Wu, S.S.-I., C.D.K.), and Pathology and Laboratory Medicine (B.R., P.E., H.V., G.S.), the Child and Family Research Institute (M.T.-G., C. Shyr, C.J.R., G.A.H., X.C.Y., A.P.B., J.J.Y.L., B.I.D., L.A., M.B.C., M.D., J.D., J.M.F., I.G., S.L., M.M., D.M., J.R., K.R.S., K.S., S.E.T., M.I.V.A., John Wu, P.E., A.M.L., H.V., S.S.-I., G.S., W.W.W., C.D.K.), and the Division of Endocrinology, Adult Metabolic Diseases Clinic (A. Mattman, S. Sirrs), University of British Columbia, and the Divisions of Biochemical Diseases (G.A.H., R.S., B.S., S.S.-I., C.D.K.), Pediatric Neurology (M.B.C., M.D., A. Michoulas, K.S.), Pediatric Nephrology (J.D.), Pediatric Endocrinology (D.M.), and Immunology (S.E.T.) and the Division of Hematology, Oncology and Transplantation, Michael Cuccione Childhood Cancer Research Program (J.R., K.R.S., John Wu), BC Children's Hospital, Vancouver, the Department of Pathology and Laboratory Medicine, Hospital for Sick Children, University of Toronto, Toronto (J.C.), the Department of Biological and Computing Sciences, University of Alberta (R.M., D.W.), and the National Institute for Nanotechnology (D.W.), Edmonton, AB, and the Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC (M. Abdelsayed, P.R.) - all in Canada; the Division of Genetics, Department of Pediatrics, King Saud Bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia (M. Alfadhel); the Division of Metabolism and Children's Research Center, University Children's Hospital Zurich, Zurich (M.R.B., P.B.), and the Departmen



Whole-exome sequencing has transformed gene discovery and diagnosis in rare diseases. Translation into disease-modifying treatments is challenging, particularly for intellectual developmental disorder. However, the exception is inborn errors of metabolism, since many of these disorders are responsive to therapy that targets pathophysiological features at the molecular or cellular level.


To uncover the genetic basis of potentially treatable inborn errors of metabolism, we combined deep clinical phenotyping (the comprehensive characterization of the discrete components of a patient's clinical and biochemical phenotype) with whole-exome sequencing analysis through a semiautomated bioinformatics pipeline in consecutively enrolled patients with intellectual developmental disorder and unexplained metabolic phenotypes.


We performed whole-exome sequencing on samples obtained from 47 probands. Of these patients, 6 were excluded, including 1 who withdrew from the study. The remaining 41 probands had been born to predominantly nonconsanguineous parents of European descent. In 37 probands, we identified variants in 2 genes newly implicated in disease, 9 candidate genes, 22 known genes with newly identified phenotypes, and 9 genes with expected phenotypes; in most of the genes, the variants were classified as either pathogenic or probably pathogenic. Complex phenotypes of patients in five families were explained by coexisting monogenic conditions. We obtained a diagnosis in 28 of 41 probands (68%) who were evaluated. A test of a targeted intervention was performed in 18 patients (44%).


Deep phenotyping and whole-exome sequencing in 41 probands with intellectual developmental disorder and unexplained metabolic abnormalities led to a diagnosis in 68%, the identification of 11 candidate genes newly implicated in neurometabolic disease, and a change in treatment beyond genetic counseling in 44%. (Funded by BC Children's Hospital Foundation and others.).

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