None of these cases had exome sequencing done to investigate the possibility of other genetic factors (https://aesnet.org/abstractslisting/williams-syndrome-and-epilepsy--a-retrospective-analysis-of-592-patients). Popp et al. identified a child with Williams syndrome and refractory infantile spasms due to denovo truncating mutation c.1200del, p.Lys401Serfs*25 in GABRA1 gene (revealed by trio exome sequencing), thus indicating that genes other than that included in the deleted region could play a significant role in the development of epilepsy in Williams syndrome cases [14]. Here, GABRA1 is linked to Down syndrome.