GBA1 and Parkinson disease: An investigation into the concurrence of PD and GD by Alcalay and others found that patients with type 1 GD were at a higher risk of developing PD than heterozygotes for GBA mutations, and both type 1 GD individuals and GBA mutation heterozygotes were at a higher risk of developing PD than non-carriers, although the difference in concurrence between type 1 GD individuals and GBA mutation heterozygotes was not statistically significant [9].