EPILEPSIA PARTIALIS CONTINUA ASSOCIATED WITH A HOMOPLASMIC MITOCHONDRIAL TRNA(SER(UCN)) MUTATION

Epilepsia partialis continua (EPC) is a rare epileptic syndrome charac terized by continuous focal seizures. We report on a 16-year-old girl who died of prolonged pharmacoresistant EPC in whom we identified a 74 72insC mutation within the mitochondrial transfer ribonucleic acid (tR NA)(Ser(UCN)). Additional symptoms included ataxia, lactic acidosis, m yopathy, sensorineural hearing loss, severe headaches, and mental reta rdation. Quantification revealed 100% mutant mitochondrial DNA (mtDNA) in the patient, 4% in her mother, and none in her half-sister. This h ighly skewed mtDNA distribution is most improbable (similar to 3 x 10( -30)) if only explained by random genetic drift. Clustering of dysfunc tional mitochondria and replicatory advantage of mutant mtDNA map play a role ire the rapid segregation towards homoplasmy within one genera tion.