Mutations in GBA are associated with familial Parkinson disease susceptibility and age at onset.
Nichols WC, Pankratz N, Marek DK, Pauciulo MW, Elsaesser VE, Halter CA, Rudolph A, Wojcieszek J, Pfeiffer RF, Foroud T, et al. Neurology. 2009 Jan 27; 72(4):310-6. Epub 2008 Nov 5.