Dominant, activating mutations in the Leucine Rich Repeat Kinase 2 (LRRK2) gene also cause PD, and surprisingly, PD patients with mutations in both LRRK2 and GBA1 genes may have a milder disease course than GBA1-PD patients in terms of motor function and olfaction (6, 7). The gene discussed is GBA1; the disease is Parkinson disease.