Aims: Our project aims at establishing the proportion of patients in whom a causal genetic finding can be identified, in a prospective cohort of children with Developmental and Epileptic Encephalopathies (DEE) followed at Children's Hospital 2 (ND2). The investigators also aim at identifying the percentage of these children in whom this approach would change current management.

Methods: A series of children diagnosed with DEE and followed at ND2 Hospital, enrolled consecutively. Exome sequencing was applied to all, with biostatistical analyses of a panel of 671 genes involved in epilepsies and developmental disorders performed in parallel at Ho Chi Minh City Vietnam National University and Geneva Genetic Medicine Division. Sanger sequencing confirmation of potentially causal variants in patients, and in parents for familial segregation. Comparison of Vietnamese and Swiss genetic findings, and multidisciplinary discussions in formal Genome Boards. Additional genetic investigations, if deemed necessary in Genome Board sessions. Clinical management adapted to genetic findings wherever applicable, and follow-up according to standard practice. One-hundred-and-fifty patients are expected to participate during the 3-year study period.