Early-Onset and Syndromic Pediatric Epilepsy in Kazakhstan: Clinical, Molecular, and Phenotypic Spectrum

Background: Pediatric epilepsy is a clinically and genetically heterogeneous group of disorders, particularly in early-onset and syndromic presentations. Data integrating molecular findings with detailed clinical phenotyping remain limited in Kazakhstan and Central Asia. Methods: We conducted a retrospective, single-center, clinically selected, referral-based case series study of 31 pediatric patients evaluated at a tertiary center in Kazakhstan for epilepsy or epilepsy-associated neurodevelopmental disorders and found to have clinically relevant or potentially relevant genetic findings. Clinical records were reviewed for demographics, age at seizure onset, seizure semiology, developmental profile, EEG, MRI, extra-neurological features, treatment response, and family history. Variants were interpreted using ACMG-based criteria, and inheritance/segregation data were incorporated where available. Results: The cohort included 15 males and 16 females. Median seizure onset was 5.0 months (IQR 2.0-13.0), and 22/31 patients (71.0%) presented within the first year of life. Developmental delay/intellectual impairment was observed in 20/31 cases (64.5%), speech delay in 17/31 (54.8%), motor delay in 15/31 (48.4%), and hypotonia in 12/31 (38.7%). Variants were identified in 23 genes, including several variants with limited or no prior support in ClinVar or peer-reviewed reports. Ion channelopathies were the largest mechanistic group (12/31, 38.7%), followed by mitochondrial/metabolic disorders (6/31, 19.4%), mTOR pathway disorders (5/31, 16.1%), and neurodevelopmental/chromatin/transcriptional disorders (4/31, 12.9%). SCN1A was the most recurrent gene (8/31, 25.8%) and showed a broad phenotypic continuum from Dravet-compatible to non-Dravet presentations. EEG and MRI abnormalities were common and often syndromic in pattern. Treatment response was frequently partial or poor, although selected genotype-linked treatment observations were noted in PRRT2 (carbamazepine), PNPO (pyridoxine), and one SCN1A case (stiripentol). Conclusions: This study expands the clinicogenetic characterization of pediatric epilepsy cases with clinically relevant or potentially relevant genetic findings in Kazakhstan and highlights the value of integrated molecular, phenotypic, and segregation analysis in underrepresented populations.