GBA1 and Parkinsonism: While, on an individual basis, patients with LBD carrying GBA1 mutations are clinically indistinguishable from those with sporadic disease, as a group, patients with parkinsonism who are either homozygous or heterozygous for GBA1 mutations, have an earlier age of onset, faster progression, and more pronounced cognitive decline than those without mutations [37,38,39].