The patient harbouring a single large‐scale mtDNA deletion (patient 7) did not have epilepsy which is entirely consistent with previous reports in the literature [14], and the other patient (patient 10) that did not have epilepsy harboured POLG mutations and had a primarily chronic progressive external opthalmoplegia (CPEO) phenotype and was elderly when he died. Here, POLG is linked to External ophthalmoplegia.