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Published on: August 15, 2019
Natural History and Developmental Trajectories of Individuals With Disease-Causing Variants in STXBP1
Kim M Thalwitzer1, Jan H Driedger1, Julie Xian1
1From the Division of Pediatric Epileptology (K.M.T., J.H.D., A.S., J.S., S.S.), Pediatric Neurology and Metabolic Medicine (A.S., S.F.G., J.S., S.K., G.F.H., M.R.), Center for Pediatrics and Adolescent Medicine, University Hospital Heidelberg, Germany; The Epilepsy NeuroGenetics Initiative (ENGIN) (K.M.T., J.X., S.M.R., K.R.S., I.H.), Division of Neurology (J.X., S.M.R., K.R.S., I.H.), and Department of Biomedical and Health Informatics (DBHi) (J.X., I.H.), Children's Hospital of Philadelphia, PA; Epilepsy Center Kleinwachau (P.Z.), Radeberg, Germany; Department of Neuropediatrics and Children's Research Center (B.K.B., G.R.), University Children's Hospital Zurich, University of Zurich; Department of Pediatric Neurology (B.K.B.), Children's Hospital of Eastern Switzerland, Sankt Gallen; Department of Pediatric Neurology and Developmental Medicine (A.N.D.), University Children's Hospital Basel UKBB, Switzerland; Department of Neurology (C.K.), Klinikum Osnabrück; Epilepsy Center (C.K.), Münster-Osnabrück, Campus Osnabrück; Department of Pediatrics (J.A.), Christophorus Hospital Coesfeld; Epilepsy Center Kork (A.W.-K.), Clinic for Children and Adolescents, Kehl-Kork; Department of Neuropediatrics (A.v.B., M.L.), University Medical Center Schleswig-Holstein, Kiel University (CAU); Center for Social Pediatrics (A.P.), Johannes Wesling Klinikum Minden; Department of Pediatric Neurology and Developmental Medicine (M.A.), University Children's Hospital, Tübingen, Germany; Department of Pediatric Neurology (H.M.H.B.), Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, the Netherlands; Department of Pediatrics (O.M.D.), Clemenshospital Münster; Department of Pediatrics (J.D.), University Medical Center Hamburg-Eppendorf; Division of Pediatric Neurology (E.H.), Department of Pediatrics and Adolescent Medicine, University Medical Center Göttingen; Kinderärzte Ammersee (I. Breitweg), Neubruch 1, Inning an Ammersee; Department of Neuropediatrics (D.D.), University Hospital Giessen; Department of Neuropediatrics (H.E.), Klinikum Esslingen; Division of Neuropediatrics (J.G.-A.), Hospital for Children and Adolescents, University Hospital Leipzig, Germany; Department of Neuropediatrics (M.P.), Children University Hospital and Paracelsus Medical University, Salzburg, Austria; Department of Neuropediatrics (J.-U.S.), Gemeinschaftskrankenhaus Herdecke; Department of Pediatrics and Adolescent Medicine (D.M.), and Center for Social Pediatrics (D.M.), University Hospital Erlangen, Friedrich-Alexander-Universität (FAU); Department of Pediatric Neurology (C.W.), SRH Zentralklinikum Suhl; Department of Pediatric Neurology (C.P.), and Center for Chronically Sick Children (C.P.), Charité-Universitätsmedizin Berlin; Department of Pediatric Neurology (C.L.-N.), Klinikum Mutterhaus der Borromäerinnen gGmbH, Trier; Séguin-Clinic for Persons with Severe Intellectual Disability (P.M.), Epilepsy Centre Kork; Medical Faculty (P.M.), University of Freiburg; Institute of Human Genetics (K.P., J.R.L.), University of Leipzig Medical Center; Sana-Krankenhaus Düsseldorf-Gerresheim (I.B.-H.), Academic Teaching Hospital der Heinrich-Heine-University Düsseldorf; Department of Neuropediatrics (K.E.), Sankt Elisabeth, KJF Klinik, Neuburg an der Donau; Department of Neuropediatrics (W.F.), Children's Hospital, University of Bonn; Center of Rare Diseases (J.R.L.), University of Leipzig Medical Center; Klinikum Aschaffenburg-Alzenau (E.R.); Department of Neuropediatrics (B.K.), Klinikum Frankfurt Höchst GmbH; Department of Neuropediatrics (T.L.), University Children's Hospital, Klinikum Oldenburg; Department of Neuropediatrics (H.S.), Klinikum Wolfsburg; Kinderneurologie Thies (B.T.), Lüneburg; Sozialpädiatrisches Zentrum Coburg (F.v.D.); Clinic for Pediatric Kidney-, Liver- and Metabolic Diseases (S.I.), Hannover Medical School; Division of Pediatric Neurology and Developmental Medicine (I. Borggraefe), Department of Pediatrics, University Hospital of the Ludwig-Maximilians-University of Munich; Department of Pediatrics (G.C.), Evangelisches Klinikum Bethel, University Hospital Owl, University Bielefeld; Institute of Human Genetics (D.W.), Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Germany; and Department of Neurology (I.H.), University of Pennsylvania Perelman School of Medicine, Philadelphia.
Background And Objectives:
Pathogenic variants in STXBP1 are among the major genetic causes of neurodevelopmental disorders. Despite the increasing number of individuals diagnosed without a history of epilepsy, little is known about the natural history and developmental trajectories in this subgroup and endpoints for future therapeutic studies are limited to seizure control.
Methods:
We performed a cross-sectional retrospective study using standardized questionnaires for clinicians and caregivers of individuals with STXBP1-related disorders capturing medical histories, genetic findings, and developmental outcomes. Motor and language function were assessed using Gross Motor Function Classification System (GMFCS) scores and a speech impairment score and were compared within and across clinically defined subgroups.
Results:
We collected data of 71 individuals with STXBP1-related disorders, including 44 previously unreported individuals. Median age at inclusion was 5.3 years (interquartile range 3.5-9.3) with the oldest individual aged 43.8 years. Epilepsy was absent in 18/71 (25%) of individuals. The range of developmental outcomes was broad, including 2 individuals presenting with close to age-appropriate motor development. Twenty-nine of 61 individuals (48%) were able to walk unassisted, and 24/69 (35%) were able to speak single words. Individuals without epilepsy presented with a similar onset and spectrum of phenotypic features but had lower GMFCS scores (median 3 vs 4, p < 0.01) than individuals with epilepsy. Individuals with epileptic spasms were less likely to walk unassisted than individuals with other seizure types (6% vs 58%, p < 0.01). Individuals with early epilepsy onset had higher speech impairment scores (p = 0.02) than individuals with later epilepsy onset.
Discussion:
We expand the spectrum of STXBP1-related disorders and provide clinical features and developmental trajectories in individuals with and without a history of epilepsy. Individuals with epilepsy, in particular epileptic spasms, and neonatal or early-onset presented with less favorable motor and language functional outcomes compared with individuals without epilepsy. These findings identify children at risk for severe disease and can serve as comparator for future interventional studies in STXBP1-related disorders.
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