LRRK2 and Parkinson disease: Olfaction has been demonstrated to be unimpaired in homozygous and compound heterozygous carriers of Parkin mutations (Alcalay et al., 2011; Khan et al., 2004) but impaired in LRRK2 parkinsonian carriers (Healy et al., 2008; Saunders-Pullman et al., 2011; Silveira-Moriyama et al., 2008, 2010), although not to the same extent as in sporadic PD.