Clinical and genetic features in patients with reflex bathing epilepsy

Objective: To describe the clinical and genetic findings in a cohort of subjects with bathing epilepsy, a rare form of reflex epilepsy. Methods: We investigated by Sanger and targeted re-sequencing the SYN1 gene in 12 individuals from 10 different families presenting with seizures primarily triggered by bathing or showering. Additional twelve subjects with hot-water epilepsy were also screened. Results: In all families with bathing epilepsy we identified 8 distinct pathogenic or likely pathogenic variants and 2 variants of unknown significance in SYN1, nine of which are novel. Conversely, none of the subjects with hot-water epilepsy displayed SYN1 variants. In mutated subjects, seizures were typically triggered by showering or bathing regardless of the water temperature. Additional triggers included fingernail-clipping, hair-cutting, or watching someone take a shower. Non-provoked seizures and a variable degree of developmental delay were also common. Conclusion: bathing epilepsy is genetically distinct reflex epilepsy mainly caused by SYN1 mutations.