Hemiconvulsion–Hemiplegia–Epilepsy Syndrome Associated with SARS-CoV-2 Infection and a Heterozygous IRF3 Variant in a 10-month-old Girl: A Case Report

Hemiconvulsion-hemiplegia-epilepsy (HHE) syndrome is a rare pediatric epilepsy syndrome characterized by prolonged focal febrile seizures, postictal hemiparesis, and progressive unilateral brain injury, often followed by chronic epilepsy. We report a previously healthy 10-month-old girl who presented with a prolonged left-sided focal fever-associated seizure. She tested positive for SARS-CoV-2 but did not meet criteria for multisystem inflammatory syndrome in children. On admission, she had left-sided flaccid hemiparesis. Brain MRI showed mild diffusion restriction and marked hyperperfusion of the right hemispheric gray matter, most prominently in the frontal, temporo-occipital, and hippocampal regions. EEG showed high-amplitude slowing over the right hemisphere without epileptiform discharges. No further seizures occurred, and long-term antiseizure treatment was not required. At 9-month follow-up, the patient was seizure-free and developmentally age-appropriate, but the hemiparesis persisted. Serial MRI showed progressive right hemispheric cortical and subcortical atrophy and hippocampal sclerosis. Extensive diagnostic workup found no other structural, infectious, or metabolic cause. This case illustrates the classical biphasic course of HHE syndrome and highlights the diagnostic value of early MRI, EEG, and genetic testing. The patient carried a paternally inherited heterozygous <i>IRF3</i> variant, a gene essential for innate antiviral immunity. Although causality cannot be established, the temporal association with SARS-CoV-2 infection and an <i>IRF3</i> variant suggests a possible genetic predisposition to infection-triggered injury. Continued clinical vigilance and long-term follow-up are essential, as epilepsy develops in most children with HHE. Greater awareness of this syndrome may support earlier recognition and timely rehabilitation to optimize functional outcomes.