This study assesses the prevalence of genetic developmental and epileptic encephalopathies (DEEs) in Italy,  covering diagnoses performed at  15 epilepsy centres over 11 years. The analysis was extended to 98 genes associated with these conditions. 1,568 patients with DEE caused by specific genetic variants were identified, leading to an estimated prevalence rate of 2.6 per 100,000 people. Diagnoses increased significantly, showing a more than tenfold rise from 2012 to 2022. The average age at diagnosis was 11.2 years, and most genetic variants showed an autosomal dominant inheritance pattern (meaning only one gene copy is needed to inherit the condition). The most commonly affected genes were SCN1A, KCNQ2, and SCN2A. This data provide an estimate of the magnitude of the medical burden related the genetic conditions gathered under the definition of DEEs and can support decision-makers in planning development programs for targeted therapies, clinicians and patients associations in establishing disease-specific registries and natural history studies. (By Dr. Davide Mei, https://jmg.bmj.com/content/early/2024/11/28/jmg-2024-110328 )