Mutations in leucine-rich repeat kinase 2 (LRRK2), the main risk factor for autosomal dominantly inherited PD, are also associated with IBD [38], and have been associated with potentiated TNFα responses [39,40] and higher levels of TNFα have been found in CSF from asymptomatic carriers of the most common LRRK2 G2019S mutation [41]. Here, TNF is linked to inflammatory bowel disease.