Researchers from centers in Belgium and Australia analyzed 80 patients with unexplained neonatal or early infantile seizures and associated psychomotor retardation for KCNQ2 mutations. Seven different heterozygous KCNQ2 mutations were found in eight patients (8/80; 10%); six mutations arose de novo. No KCNQ3 mutations were found. The eight KCNQ2 encephalopathy patients had onset of intractable seizures with tonic component in the first week of life. Seizures resolved by age 3 years but the children had profound or severe psychomotor impairment. EEG at onset showed a multifocal epileptiform activity. Early brain MRI showed hyperintensities in the basal ganglia and thalamus that later resolved. KCNQ2 screening should be included in the diagnostic workup of refractory neonatal seizures of unknown origin. 
COMMENT. Mutations in the voltage gated K(+)-channel gene KCNQ2 cause benign familial neonatal convulsions, the majority having a favorable outcome.  Reports of patients with a poor outcome are infrequent. Dedek K and associates (Epilepsy Res 2003;54(l):21-27) of Hamburg, Germany reported two children in an Italian family with neonatal convulsions and KCNQ2 mutations, the index patient having a poor outcome and therapy-resistant epilepsy. The present report is supportive of the association of some KCNQ2 mutations with an infantile epileptic encephalopathy complicated by psychomotor impairment and refractory seizures.