Biallelic pathogenic variants of PARS2 cause developmental and epileptic encephalopathy with spike-and-wave activation in sleep.

These findings widen the genetic heterogeneity of DEE-SWAS, including PARS2 as a causative gene in this syndromic entity, and highlight the importance of prolonged sleep EEG recording for the recognition of SWAS as a possible electroclinical evolution of PARS2-related DEE.