Insertion of leucine at position 776, in the second transmembrane domain. Benign familial neonatal convulsions Clinical Autosomal dominant inheritance. Clonic seizures begin within days of birth and stop in weeks to months. Seizures may be generalized or partial. Apneic spells occur.
Neurologic development is normal.
A 5 base pair insertion in one pedigree causes a premature stop codon , deleting more than 300 amino acid residues. There is a defect in potassium current. Partial impairment of potassium-dependent repolarization causes epilepsy. KCNQ1 causes long QT syndrome. Clinical Many seizure phenotypes.