1. Kennedy Krieger Institute , Baltimore, MD , USA
2. Johns Hopkins University School of Medicine Department of Psychiatry and Behavioral Sciences, , Baltimore, MD , USA
3. Johns Hopkins University School of Medicine Department of Genetic Medicine, , Baltimore, MD , USA
4. Johns Hopkins University School of Medicine Department of Pediatrics, , Baltimore, MD , USA
5. University of Iceland Faculty of Medicine, , Reykjavik , Iceland
6. Landspitali University Hospital , Reykjavik , Iceland
7. Johns Hopkins University School of Medicine Department of Neurology, , Baltimore, MD , USA