In light of the reported c.64T>C, p.Trp22Arg NDUFB3 cases, cardiac screening was performed, revealing Wolff–Parkinson–White (WPW) syndrome in patient 8, a rare cardiac conduction defect which is over-represented in patients with mitochondrial disease.23 The initial manifestation of WPW syndrome can be sudden death and the diagnosis might facilitate interventions including non-invasive risk stratification and/or therapeutic ablation.24 The gene discussed is NDUFB3; the disease is Wolff-Parkinson-White syndrome.