The current state of knowledge on de novo mutations in epileptic encephalopathies. 15-20% of patients have explanatory mutations, e.g. de novo mutations in SCN1A, STXBP1 etc. A small percentage does not have any de novo mutations. Most patients, however, carry de novo mutations in possible candidates. Collaborative studies are required to generate additional evidence for the pathogenic role of these genes. This statement is not just an empty promise. Ever since the publication of the Epi4K publication, three genes (CHD2, GNAO1, SLC35A2) have already crossed the border from candidate status to causative gene.