Beyond SNCA and LRRK2, whose contribution to PD pathogenesis is supported strongly by genetic studies, we have chosen to also study UCH-L1 gene, although its genetic link to PD has been questioned (Lincoln et al., 1999; Maraganore et al., 1999, 2004; Healy et al., 2006). The gene discussed is LRRK2; the disease is Parkinson disease.