What are the symptoms? The early seizures in the first year consist of clonic (jerking) movements, which often affect one side of the body and are prolonged. A total of 75 per cent of seizures are provoked by fever and this may follow immunisation, which is regarded as a non-specific trigger. Development during the first year of life is usually normal, but following this a range of seizures appear which include: myoclonic jerks, single or multiple muscle jerks, which may involve one part of the body or the whole bodyatypical absences with brief loss of awarenesspartial seizures, which may involve loss of awarenessnon-convulsive status where the child develops a groggy, poorly functional state. Sometime from the second year developmental slowing or regression occurs, which is often but not invariably severe. Features of autism (see entry Autism Spectrum conditions) and attention deficit hyperactivity disorder are common. A movement problem of the legs commonly appears with signs of spasticity (muscle tightness) and unsteadiness. Mild variants of this condition are occasionally seen. What are the causes? About 80 per cent of patients with Dravet syndrome have various mutations in a sodium channel gene, SCN1A, and in rare cases a GABA gene defect is found (GABRG2). How is it diagnosed? The diagnosis of Dravet syndrome is essentially clinical, based upon the evolution of typical seizures and developmental regression. The presence of the gene defect is strongly supportive evidence but not required for diagnosis and can be associated with other types of epilepsy including generalised epilepsy with febrile seizures plus (GEFS+). How is it treated? Anti-epileptic drugs are used but often not effective. Stiripentol has been advocated, usually combined with a benzodiazepine and/or sodium valproate. Comprehensive assessment and provision is required for the multiple impairments associated with Dravet syndrome. Inheritance patterns and prenatal diagnosis Inheritance patternsFamilial occurrence is rare and most are due to a new mutation. Prenatal diagnosisThis can only be discussed in rare familial situations. Is there support? Dravet Syndrome UK Tel: 08443 321 008Email: email@example.comWebsite: dravet.org.uk The Group in a Registered Charity in England and Wales No. 1128289. It provides emotional, practical and financial support for families affected by Dravet Syndrome. The Group funds medical research into Dravet Syndrome and other related genetic sodium channel epilepsies, and raises awareness and understanding of the condition within the professional community. Group details last updated October 2015. References Caraballo RH. Fejerman N. Dravet syndrome: a study of 53 patients. Epilepsy Research. 2006;70:231-38. Dravet C, Bureau M, Oguni H, et al. Severe myoclonic epilepsy in infancy (Dravet syndrome). In Roger J, Bureau M, Dravet CH, et al (Eds) Epileptic syndromes in infancy, childhood and adolescence (3rd edition). 2002; John Libbey: London, UK (p 81-103). Escayg A, Heils A, MacDonald BT, et al. A novel SCN1A mutation associated with generalized epilepsy with febrile seizures plus and prevalence of variants in patients with epilepsy. Am J Genet. 2001;68:866-73. Gennaro E. Veggiotti P. Malacarne M, et al. Familial severe myoclonic epilepsy of infancy: truncation of Nav1.1 and genetic heterogeneity. Epileptic Disord. 2003;5:21-5. Hurst DL. Epidemiology of severe myoclonic epilepsy of infancy. Epilepsia 1990;31:397-400. Incorpora G. Dravet syndrome. Ital J Pedriatr. 2009;35:27. Scheffer IE. Severe infantile epilepsies: molecular genetics challenge clinical classification. Brain. 2003;126:513-4. Wiznitzer M. Effects of vaccination on onset and outcome of Dravet syndrome: a retrospective study. Lancet Neurology. 2010;9:559-61.