To present a case of a patient with epilepsy and autism spectrum disorder who was found to have a genetic epileptic encephalopathy. Genetic diagnosis directly impacted his course of treatment.

Approximately 30% of patients with autism spectrum disorder have epilepsy, and the majority are focal-onset epilepsy. Our patient had a single pathogenic variant in CHD2 on the Invitae Behind the Seizure sponsored genetic sequencing panel. CHD2 is associated with autosomal dominant epileptic encephalopathy with atonic-myoclonic-absence seizures.

This is a single clinical case report of a genetic diagnosis altering clinical management of a patient with a developmental epileptic encephalopathy.

The patient is a 4-year-old boy with developmental delay and autistic traits who presented with loss of tone, perioral cyanosis and eyes open and rolled back. EEG and MRI were normal. He presented with a second event of similar semiology the following month and was started on levetiracetam. One month later he presented in status epilepticus with rightward eye deviation, full body stiffness, hands turning inwards, followed by limpness and lip-smacking. Oxcarbazepine was added to his regimen, but frequent seizures continued. Additional work-up was obtained: psychological assessment diagnosing autism spectrum disorder, non-diagnostic Fragile X testing, repeat EEG showing bifrontal and centroparietal spike and slow wave complexes, and Behind the Seizure panel showing a deletion involving the full coding sequence of CHD2. His seizures were recharacterized from focal-onset with impaired awareness to atonic-myoclonic-absence, and anti-seizure regimen was switched to include only broad-spectrum agents, currently zonisamide and cannabidiol. With tapering of oxcarbazepine, there was a decreased frequency of myoclonic seizures.

This case demonstrates an example of genetic testing providing a diagnosis that directly impacted patient care. Improved seizure control was attained when the genetic diagnosis suggested a generalized-onset epilepsy that was exacerbated by a narrow-spectrum anti-seizure medication, despite focal epileptiform discharges on EEG.