Previously, four individual case reports have identified PTPN23 gene alterations as a candidate cause of neurological disease in four unrelated individuals with severe epilepsy and neurodevelopmental delay, sometimes classified as developmental and epileptic encephalopathy (DEE; [ILAE classification]) (Table S1) [15,16,17,18]. This evidence concerns the gene PTPN23 and developmental and epileptic encephalopathy.