However, the severity of symptoms, including epilepsy and qEEG phenotypes, can be variable and affected by other differences including mosaic imprinting (milder symptoms) or haploinsufficiency of other genes with larger 15q11-q13 region deletions that encompass UBE3A and the GABAA receptor subunits (typically more severe phenotypes exacerbated by non-UBE3A pathophysiology; Minassian et al., 1998; Lossie et al., 2001; Frohlich et al., 2019a). This evidence concerns the gene UBE3A and epilepsy.