Developmental epileptic encephalopathy (DEE) in children presents significant diagnostic and management challenges. Advances in whole-exome sequencing (WES) have enabled the identification of rare genetic variants, offering new insights into these complex conditions. Here, we report a 2.5-year-old girl with refractory epilepsy and DEE, in whom WES revealed a novel homozygous SULT4A1 splice-site variant. Although the SULT4A1 variant likely contributed to her condition, the later emergence of motor and speech delay in a sibling with the same mutation suggests variable expressivity or age-dependent onset, rather than incomplete penetrance. The patient partially responded to immunotherapy but continued to experience breakthrough seizures and developmental delays, highlighting the challenges in managing such disorders. This case underscores the importance of genetic testing, functional studies, and genetic counseling in the diagnosis and treatment of rare neurodevelopmental disorders.
Keywords: NMDA receptor; SULT4A1; developmental epileptic encephalopathy (DEE); splice-site variant; whole-exome sequencing (WES).