BACKGROUND: The underlying genetic abnormalities of rare familial idiopathic 
epilepsy have been identified, such as mutation in KCNQ2, a K(+) channel gene. 
Yet, few genetic abnormalities have been reported for commoner epilepsy, i.e., 
sporadic idiopathic epilepsy, which share a phenotype similar to those of 
familial epilepsy.
OBJECTIVE: To search for the genetic cause of seizures in a girl with the 
diagnosis of non-familial benign neonatal convulsions, and define the 
consequence of the genetic abnormality identified.
METHODS: Genetic abnormality was explored within candidate genes for benign 
familial neonatal and infantile convulsions, such as KCNQ2, 3, 5, KCNE2, SCN1A 
and SCN2A. The electrophysiological properties of the channels harboring the 
identified mutation were examined. Western blotting and immunostaining were 
employed to characterize the expression and intracellular localization of the 
mutant channel molecules.
RESULTS: A novel heterozygous mutation (c.910-2delTTC or TTT, Phe304del) of 
KCNQ2 was identified in the patient. The mutation was de novo verified by 
parentage analysis. The mutation was associated with impaired functions of KCNQ 
K(+) channel. The mutant channels were expressed on the cell surface.
CONCLUSION: The mutant Phe304del of KCNQ2 leads to null function of the KCNQ 
K(+) channel but the mutation does not alter proper channel sorting onto the 
cell membrane. Our findings indicate that the genes responsible for rare 
inherited forms of idiopathic epilepsy could be also involved in sporadic forms 
of idiopathic epilepsy and expand our notion of the involvement of molecular 
mechanisms in the more common forms of idiopathic epilepsy.