Abstract
Cannabidiol (CBD) is a compound found specifically in the cannabis plant. Although a clinical trial for intractable epilepsy started in Japan in 2023, it is also available in the market as a dietary supplement. Herein, we report two cases of identical twins with developmental and epileptic encephalopathy with STXBP1 gene mutation who achieved seizure suppression through different regimens of CBD supplementation. The observation that different trace ingredients produced different effects in patients with identical genetic backgrounds is a crucial finding that has implications for the future regulation and clinical application of cannabinoid products.