MECP2 and atypical Rett syndrome: Of note, we also detected mosaic pathogenic variants in several additional epilepsy-related genes including some of the GABA receptor genes, GABRA1 (0.125; 95% CI, 0.016–0.384) and GABRG2 (0.042; 95% CI, 0.001–0.211); GRIN2B (0.063; 95% CI, 0.002–0.302), which encodes the glutamate-binding NR2B subunit of the N-methyl-d-aspartate receptor; the potassium channel gene KCNQ2 (0.006; 95% CI, 0.001–0.035); and MECP2 (0.011; 95% CI, 0.0003–0.062) in a male with atypical Rett syndrome (Table 2).