Exome data of developmental and epileptic encephalopathy patients reveals de novo and inherited pathologic variants in epilepsy-associated genes

•Nine patients harbor pathological (P) or likely pathological (LP) mutations (31%) and three patients have VUS variants (10%) out of 29 DEE patients.•De novo mutations were identified in SCN2A, KCNMA1 and MECP2 genes.•Four novel variations were detected in SCN2A, SCN1A, ATP1A2 and KCNQ2 genes.•Two patients have autosomal recessive inherited mutations in NPC2 and CLN6 genes.•MD simulations revealed the destructive effects of the mutations on protein structures.