Abstract
BackgroundMitochondrial diseases caused by mutations in mitochondrial DNA (mtDNA) affect tissues with high energy demand. Epilepsy is one of the manifestations of mitochondrial dysfunction when the brain is affected. We have studied here 79 Finnish patients with epilepsy and who have maternal first- or second-degree relatives with epilepsy, sensorineural hearing impairment or diabetes mellitus.MethodsThe entire mtDNA was studied by using conformation sensitive gel electrophoresis and PCR fragments that differed in mobility were directly sequenced.ResultsWe found a common nonsynonymous variant m.15218A > G (p.T158A, MTCYB) that occurs in haplogroup U5a1 to be more frequent in patients with epilepsy. The m.15218A > G variant was present in five patients with epilepsy and in four out of 403 population controls (p = 0.0077). This variant was present in two branches in the phylogenetic network constructed on the basis of mtDNA variation among the patients. Three algorithms predicted that m.15218A > G is damaging in effect.ConclusionsWe suggest that the m.15218A > G variant is mildly deleterious and that mtDNA involvement should be considered in patients with epilepsy and who have a maternal history of epilepsy, sensorineural hearing impairment or diabetes mellitus.
Highlights
Mitochondrial diseases caused by mutations in mitochondrial DNA affect tissues with high energy demand
Other mitochondrial diseases which can present with seizure symptoms are neuropathy, ataxia, retinitis pigmentosa syndrome and Kearns-Sayre syndrome [4]
Blood samples were obtained from 165 patients and 79 patients were selected if the number of maternal relatives with epilepsy, diabetes or sensorineural hearing impairment was ≥ 2 (38 patients) or if a family history score was ≥ 0.1 in families with one maternal relative with epilepsy or sensorineural hearing impairment (41 patients)
Summary
Mitochondrial diseases caused by mutations in mitochondrial DNA (mtDNA) affect tissues with high energy demand. Epilepsy is one of the manifestations of mitochondrial dysfunction when the brain is affected. Epilepsy is a frequent manifestation of mitochondrial disorders, as the brain is often severely affected in these diseases [3]. The most common mitochondrial DNA (mtDNA) mutation causing epilepsy is m.8344A > G in the MTTK gene. It causes MERRF syndrome (myoclonus epilepsy associated with ragged red fibers) [6]. Other mitochondrial diseases which can present with seizure symptoms are neuropathy, ataxia, retinitis pigmentosa syndrome and Kearns-Sayre syndrome [4]. Mitochondrial oxidative stress may play a role in epileptogenesis by virtue of affecting neuronal excitability [9]
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