LRRK2 and Parkinson disease: Genome-wide linkage scans and exome sequencing of well-characterized PD families have been successful in discovering disease-causing mutations in dominant (SNCA, LRRK2, VPS35 and the recent TMEM230), recessive (PARK2, PINK1, DJ1, DNAJC6) [2–4] and X-linked (RAB39B) PD genes [5, 6].