Haploinsufficiency of LETM1, which encodes a mitochondrial protein that is involved in ion transport, is thought to underlie the seizures and some other features of classical WHS, but how LETM1 haploinsufficiency contributes to seizure presentation or indeed whether individuals with WHS exhibit any LETM1-dependent phenotypes has not been fully elucidated. This evidence concerns the gene LETM1 and Wolf-Hirschhorn syndrome.