MT-TK and MERRF: Mutations in MT-TK and MT-TL1 genes have been reported in MERRF/MELAS and MERRF/Kearns-Sayre syndrome overlap syndromes [45,46]; moreover m.8344A > G mutation has also been observed in LS, isolated myoclonus, isolated myopathy and multiple symmetric lipomatosis, in which ataxia has been reported in some cases [5,47].