Dravet syndrome diagnosed in adults

Dravet syndrome is a rare and severe developmental and epileptic encephalopathy, caused by pathogenic variants of SCN1A in 80%-90% of patients. It is a clinical diagnosis typically made in childhood, but many adults who may never have had appropriate genetic testing remain undiagnosed. We present four patients with longstanding drug-resistant epilepsy and intellectual disability where genetic testing led to a diagnosis of Dravet syndrome or another SCN1A-related epilepsy syndrome. These descriptions highlight important and atypical clinical features. There are also challenges including interpreting variants of uncertain significance, and considering the function of the SCN1A variant. It is important to recognise Dravet syndrome in adults, since inappropriate antiseizure medications increase the risk of seizures. As precision medicine and gene therapies advance, it is increasingly important to make an accurate clinical and molecular diagnosis. Neurologists should consider Dravet syndrome in adults with early-onset epilepsy and intellectual disability.