Complex/polygenic inheritance in most patients, de novo pathogenic variants have been found in some patients with this syndrome and intellectual impairment.
In patients without encephalopathy, with complex/polygenic genetic etiology, no causal pathogenic gene variant is expected to be found. However, in patients with encephalopathy, several pathogenic gene variants have been identified including CHD2, SYNGAP1, NEXMIF and others.
A family history of seizures/epilepsy is common. Approximately 20% of individuals have a family history of idiopathic generalized epilepsy and nearly half of patients have a family history of genetic epilepsy with febrile seizures plus spectrum.