Functional evidence for SCN8A splice-donor variant c.4419+1 A > G causing loss of function

We report a child with severe developmental and epileptic encephalopathy carrying a rare SCN8A splice‑site variant. Although its pathogenicity was initially unclear, a minigene assay demonstrated aberrant splicing, indicating a loss‑of‑function mechanism. Integrated clinical, genetic and functional evidence classified the variant as pathogenic, underscoring the importance of splicing assays for interpreting rare SCN8A variants.