Table 2.

KCNQ3-Related Disorders: Frequency of Select Features 1

PhenotypeFeature% of Persons w/Feature 2Comment
KCNQ3-SLFNE Epilepsy>90%
  • Age of onset of seizures is between 2-8 days of life; spontaneously disappear between age 1-12 mos in otherwise healthy infant.
  • Seizures are generally brief, lasting 1-2 minutes.
  • Seizure types incl tonic or apneic episodes, focal clonic activity, & autonomic changes.
Normal psychomotor development>90%Rare reports of DD or ID
KCNQ3-SLFIE Epilepsy100% (6/6)
  • Age of onset of seizures is w/in 1st yr of life, beyond neonatal period, & seizures disappear in 1-2 years.
  • Seizures are generally brief, lasting ~2 minutes; they are usually focal but can be also generalized.
Normal psychomotor development100% (6/6)
KCNQ3-NDD Developmental delays / intellectual disability>90%Moderate-to-severe ID
Autism spectrum disorder~20% (12/59)Autistic features incl stereotypies, mouthing nonfood objects, & aggressive, impulsive, & self-injurious behaviors. 3 Given that ASD features (& other details about phenotype) in larger cohorts of ID/DD are not reported, this figure may be underestimated.
Epilepsy~20%Even persons w/o clinical seizures often have abundant sleep-activated epileptic activity on EEG recordings.

ASD = autism spectrum disorder; DD = developmental delay; ID = intellectual delay; NDD = neurodevelopmental disorder; SLFIE = self-limited familial infantile epilepsy; SLFNE = self-limited familial neonatal epilepsy

1.
2.

Percentages are based on nearly 140 reported symptomatic individuals with heterozygous pathogenic variants only and do not include individuals with biallelic pathogenic variants in KCNQ3.

3.

From: KCNQ3-Related Disorders

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