Results:
From approximately 600 patients seen from January 2017 to June 2018 at a single academic epilepsy center, 64 probands and 2 affected relatives (32 males, mean age = 31 years ± 10) were selected and clinically tested. Fourteen probands (14/64 = 22%; 4 males, mean age = 32 years ± 10) were found to have pathogenic or likely pathogenic variants in the following genes: SCN1A, GABRB3, UBE3A, KANSL1, SLC2A1, KCNQ2, SLC6A1, HNRNPU, STX1B, SCN2A, PURA, and CHD2. Six variants arose de novo, and the inheritance was not determined in 8. Nine probands (64%) had severe or profound intellectual disability, and 5 (35%) had autistic features. Eight patients (57%) had a diagnostic change from presumptive clinical diagnosis prior to genetic testing.