Patient outcomes in <scp> <i>KCNQ2</i> </scp> developmental and epileptic encephalopathy

The aim of this study was to review and summarize the literature describing clinically observed or caregiver-reported and patient-reported KCNQ2 developmental and epileptic encephalopathy (DEE) outcomes. Three online databases and selected congress proceedings were searched (August 2023). Case reports and series, observational studies, non-randomized and single-arm trials, and registries and databases reporting seizure-related and non-seizure-related outcomes in patients aged 18 years or younger with KCNQ2 DEE were eligible for inclusion. Results were summarized according to outcome type (seizure-related and non-seizure-related) and patient age. Of 92 publications reporting KCNQ2 DEE outcomes, 70 reported patient-level data, of which the most common age was younger than 5 years old. Seizures were frequently reported (69 of 70 publications for 338 patients). Seizure onset was primarily within the first week of life (n = 334 of 356 seizure events; 93.8%), with frequency commonly reported as 'multiple daily'. Seizure resolution was reported for 56.2% of patients; most (87.0%) achieved resolution by age 5 years. Seventy publications reported non-seizure-related outcomes for 289 patients. Neurological (73.3%) and developmental (52.9%) manifestations were frequently reported, with muscle tone (71.7%), gross motor (67.3%), and communication (66.6%) impairments being most common. Similar findings were observed across 23 publications reporting pooled patient data. While seizures were typically resolved in early life, non-seizure-related outcomes gained more prominence as children aged, highlighting the evolving challenges for individuals living with KCNQ2 DEE.