MSH6 and Leigh syndrome: Barrow et al.3studied 839 individuals with LS in North West of England, reporting cumulative incidences at age 70 of 0% for MLH1, 0.7% (95% CIs, 0.0–1.4) for MSH2 and 0% for MSH6. 3These findings are comparable with our results (0.4% for MLH1, 1.3% for MSH2/EpCAM and 0.2% for MSH6 at age 70), although the low incidence in their study may reflect broader inclusion of individuals without confirmed PVs.