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Clinical and molecular genetics of myoclonic–astatic epilepsy and severe myoclonic epilepsy in infancy (Dravet syndrome)

  • Ingrid E Scheffer
    Correspondence
    Corresponding author. Epilepsy Research Institute, Austin and Repatriation Medical Centre, Level 1, Neurosciences Building, Repatriation campus, Banksia Street, West Heidelberg 3081, Victoria, Australia. Tel.: +61-3-9496-2737; fax: +61-3-9496-2291
    Affiliations
    Epilepsy Research Institute, University of Melbourne, Austin and Repatriation Medical Centre and Royal Children's Hospital, Melbourne, Victoria, Australia

    Monash Medical Centre, Melbourne, Victoria, Australia
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  • Robyn Wallace
    Affiliations
    Department of Cytogenetics and Molecular Genetics, Centre for Medical Genetics, Women's and Children's Hospital, North Adelaide, South Australia, Australia

    Department of Paediatrics, University of Adelaide, Adelaide, South Australia, Australia
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  • John C Mulley
    Affiliations
    Department of Cytogenetics and Molecular Genetics, Centre for Medical Genetics, Women's and Children's Hospital, North Adelaide, South Australia, Australia

    Department of Genetics, University of Adelaide, Adelaide, South Australia, Australia
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  • Samuel F Berkovic
    Affiliations
    Epilepsy Research Institute, University of Melbourne, Austin and Repatriation Medical Centre and Royal Children's Hospital, Melbourne, Victoria, Australia
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      Abstract

      The majority of severe epileptic encephalopathies of early childhood are symptomatic where a clear etiology is apparent. There is a small subgroup, however, where no etiology is found on imaging and metabolic studies, and genetic factors are important. Myoclonic–astatic epilepsy (MAE) and severe myoclonic epilepsy in infancy (SMEI), also known as Dravet syndrome, are epileptic encephalopathies where multiple seizure types begin in the first few years of life associated with developmental slowing. Clinical and molecular genetic studies of the families of probands with MAE and SMEI suggest a genetic basis. MAE was originally identified as part of the genetic epilepsy syndrome generalized epilepsy with febrile seizures plus (GEFS+). Recent clinical genetic studies suggest that SMEI forms the most severe end of the spectrum of the GEFS+. GEFS+ has now been associated with molecular defects in three sodium channel subunit genes and a GABA subunit gene. Molecular defects of these genes have been identified in patients with MAE and SMEI. Interestingly, the molecular defects in MAE have been found in the setting of large GEFS+ pedigrees, whereas, more severe truncation mutations arising de novo have been identified in patients with SMEI. It is likely that future molecular studies will shed light on the interaction of a number of genes, possibly related to the same or different ion channels, which result in a severe phenotype such as MAE and SMEI.

      Keywords

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