- The mitochondrial 13513G>A mutation is most frequent in Leigh syndrome combined with reduced complex I activity, optic atrophy and/or Wolff-Parkinson-White. Ruiter, E.M., Siers, M.H., van den Elzen, C., van Engelen, B.G., Smeitink, J.A., Rodenburg, R.J., Hol, F.A. Eur. J. Hum. Genet. (2007)