Seizures in Sotos syndrome: Phenotyping in 49 patients

We aimed to describe the phenotypic spectrum of seizures in Sotos syndrome, a genetic condition involving overgrowth, macrocephaly, dysmorphic features, and learning disability, in which 60%‐90% have NSD1 pathogenic variants. Patients were recruited from clinics and referral from support groups. Those with seizures and a clinical diagnosis of Sotos syndrome were included. Phenotyping data were collected via structured clinical interview and chart review. Forty‐nine patients were included. Twenty had NSD1 testing results available; of these, 15 (75%) had NSD1 pathogenic variants. Seizure onset age ranged from 3 months to 12 years. Staring spells (absence or focal impaired awareness seizure) were the most frequently reported semiology (33/49; 67%), followed by febrile seizures (25/49; 51%) and afebrile bilateral tonic‐clonic seizures (25/49; 51%). Most patients (33/49; 67%) had multiple seizure types. The majority (33/49; 67%) had seizures controlled on a single antiseizure medication or no medication. Nine (18%) had drug‐resistant epilepsy. Epilepsy syndromes included febrile seizures plus, Lennox‐Gastaut syndrome, childhood absence epilepsy, and generalized tonic‐clonic seizures alone. The seizure phenotype in Sotos syndrome most commonly involves staring spells, afebrile tonic‐clonic seizures or febrile convulsions; however, other seizure types may occur. Seizures are typically well‐controlled with medication, but drug‐resistant epilepsy occurs in a minority.