The epileptology of Wiedemann-Steiner syndrome: Electroclinical findings in five patients with KMT2A pathogenic variants

Wiedemann-Steiner Syndrome (WSTS) is a rare chromatinopathy caused by pathogenic variants in KMT2A. WSTS is characterized by neurodevelopmental disorders and distinct dysmorphic features. Epilepsy has been reported in only 33 individuals with WSTS, with only limited clinical details described.We identified patients with pathogenic KMT2A variants and epilepsy, and performed thorough phenotyping.Five patients were identified, all of whom presented with developmental and epileptic encephalopathy (DEE). Epilepsy syndromes observed included Lennox-Gastaut syndrome [2], infantile epileptic spasms syndrome, and DEE with spike-wave activation in sleep. Seizure types observed included absence, generalized tonic-clonic, myoclonic, tonic, atonic, epileptic spasms, and focal seizures.The spectrum of epilepsy phenotypes in patients with WSTS can be broad, but presentation is typically severe, usually involving a form of DEE.