Here we aimed to study the contribution of the lysosome to the pathogenesis of PD through the analysis of a group of lysosomal enzymes (β-glucocerebrosidase (β-GCase; EC 3.2.1.45), β-galactosidase (β-gal; EC 3.2.1.23), β-hexosaminidase (Hex B; EC 3.2.1.52), and Cathepsin D (CatD; EC 3.4.23.5)) in peripheral blood from sporadic PD patients in the early stages of the disease. The gene discussed is CTSD; the disease is Parkinson disease.