MSH2 and Leigh syndrome: In addition, limited data were found regarding molecular testing, with 7% of participants only having had IHC testing for MMR proteins MLH1/ MSH2 / MSH6/ PMS2, which is necessary for the diagnosis for LS. Four of the participants (57%) had loss of at least one expression of MMR proteins, and three of them were younger than 50 years old, and only one reported family history of EC.