Two siblings with early infantile myoclonic encephalopathy due to mutation in the gene encoding mitochondrial glutamate/H+ symporter SLC25A22

Aim To characterize a new subset of early myoclonic encephalopathy usually associated with metabolic etiologies with a new genetic entity.

Methods We describe two siblings with early myoclonic encephalopathy born to consanguineous parents of Arab Muslim origin from Israel. We used homozygosity mapping and candidate gene sequencing to reveal the genetic basis of the myoclonic syndrome.

Results We found a rare missense mutation in the gene encoding one of the two mitochondrial glutamate/H symporters, SLC25A22. The phenotype of early myoclonic encephalopathy was first linked to the same mutation in 2005 in patients of the same ethnicity as our family.

Conclusions Owing to the devastating nature of this encephalopathy, we focus attention on its clinical history, epileptic semiology, distinct electroencephalography features, and genetic basis. We provide the evidence that an integrated diagnostic strategy combining homozygosity mapping with candidate gene sequencing is efficient in consanguineous families with highly heterogeneous autosomal recessive diseases.