GABRB1 and Encephalopathy: Encephalopathy is characteristic of 112 IMDs (19%) that are often classified as developmental and epileptic encephalopathies (DEE) (e.g., early infantile epileptic encephalopathies due to GABRA1, GABRB1, GABRB2 or GABRB3 pathogenic variants; Supplementary Table S1).