GPI and early-onset autosomal dominant Alzheimer disease: Although cases such as KD with bilateral GPi lesions are rare, apathy is common in Parkinson's disease (Oguru et al., 2010; Pedersen, et al., 2009; Starkstein, 2009), as well as in other neurodegenerative disorders, including Huntington's and Alzheimer's disease (Bonelli and Cummings, 2008; Chow et al., 2009; Starkstein et al., 2006; Marin, 1991).