The ACMSD gene, involved in tryptophan metabolism, is mutated in a family with cortical myoclonus, epilepsy, and parkinsonism.
Martí-Massó JF, Bergareche A, Makarov V, Ruiz-Martinez J, Gorostidi A, López de Munain A, Poza JJ, Striano P, Buxbaum JD, Paisán-Ruiz C. J Mol Med (Berl). 2013 Dec; 91(12):1399-406. Epub 2013 Aug 20.