[Movement disorders].

Thanks to the application of modern techniques such as next-generation sequencing in the study of apparently non-inherited encephalopathies it has become possible to describe de novo pathogenic mutations in unsuspected genes and to define the phenotypes of these mutations. Interestingly, in most cases, their clinical signs and symptoms show a spectrum in which epileptic encephalopathy, neurodevelopmental disorder and hyperkinetic abnormal movement disorders overlap. Their pathophysiology is located in synapses (synaptopathies). This article offers a brief summary of these disorders and also includes a simple note, in honour of Dr Natalio Fejerman (1934-2018), on the so-called «benign polymorphic disorder of infancy».