Figure 1.

Detection of disease‐causing variants using a targeted gene panel (a) Forty disease‐causing variants were found in 116 patients with early‐onset epilepsy developed before 2 years of age. There were 19 pathogenic variants and 21 likely pathogenic variants. SCN1A variants, which are associated with Dravet syndrome and generalized epilepsy with febrile seizure plus, were most common (n = 16), and PRRT2 variants, which are associated with BFIE, were the second most common (n = 11). (b) Detection of disease‐causing variants and electroclinical syndrome. Among the patients that were genetically confirmed as having Dravet syndrome, 15 had a SCN1A mutation and two had a PCHD19 mutation. All patients having a PRRT2 mutation were diagnosed with BFIE. KCNQ2 mutations were found in patients with BFNS and EOEE. Others included ARX, SCN2A, STXBP1, and SCN8A in patients with EOEE, and a DEPDC5 mutation in a patient with intractable focal epilepsy. (c) Diagnostic yield in each epilepsy syndrome. BFIE showed the highest diagnostic rate with 84.6% (n = 11/13) and Dravet syndrome followed that with 81% (n = 17/21). BFNS had a 50% positive rate of detection (n = 2/4) and about a quarter of patients with EOEE had a disease‐causing variant (n = 8/29, 27.6%). BFIE, benign familial infantile epilepsy; BFNS, benign familial neonatal seizure; GEFSP, generalized epilepsy with febrile seizure plus; EOEE, early‐onset epileptic encephalopathy