In a study of 170 patients with PD (102 GBA1-PD, 38 LRRK2-PD, and 30 iPD) and 221 non-manifesting carriers (NMC) (129 GBA1-NMC, 45 LRRK2-NMC, 15 GBA1-LRRK2-NMC, and 32 healthy controls), GCase activity was lower among GBA1-PD, GBA1-NMC, and GBA1-LRRK2-NMC compared to the other groups of participants, with no correlation to clinical phenotype [151]. The gene discussed is LRRK2; the disease is Parkinson disease.