Epileptic seizures and EEG findings in 3p deletion syndrome involving SLC6A1

Abstract

3p Deletion syndrome is a rare genetic disorder characterized by intellectual disability, growth delay, hypotonia, and distinctive facial features, with considerable phenotypic variability. Previous reports have highlighted the significance of deletions within the 3p25.3 region contributing to the development of Angelman-like features, such as stereotypic movements, a happy demeanor, epilepsy, and characteristic electroencephalogram (EEG) patterns. This study analyzed 22 patients of 3p deletion syndrome, focusing on epilepsy and EEG findings. A newly defined short smallest region of overlap (sSRO) within 3p25.3, encompassing approximately 52 kb and partially including SLC6A1 and SLC6A11, was associated with Angelman-like features, particularly epilepsy and EEG patterns. Patients with sSRO deletions exhibited a high incidence of seizures (60 %), characterized by myoclonic or absence seizures, with EEG showing generalized high-amplitude slow waves. In contrast, larger deletions beyond the sSRO were linked to dysmorphological features of 3p-syndrome, generalized tonic-clonic seizure, and non-specific EEG findings. These findings suggest that SLC6A1 dysfunction contributes to epilepsy and EEG abnormalities, possibly via impaired GABA transport, whereas patients with larger or non-overlapping deletions exhibited more typical 3p-syndrome features, suggesting that multiple neurological genes in the broader deletion region may independently contribute to more severe neurological phenotypes. In conclusion, it is important to consider GABA-related disorders, including a specific chromosomal abnormality known as 3p-syndrome with a microdeletion in the SRO region, when observing characteristic epilepsy and EEG findings resembling Angelman syndrome.