Several studies have established an association between PD and cathepsin activity, indicating their possible role in the etiology of the disease (Yelamanchili et al., 2011; Pišlar et al., 2018; McGlinchey et al., 2019; Pal et al., 2019; Yuan et al., 2021; Milanowski et al., 2022; Stoka et al., 2023). The gene discussed is CTSS; the disease is Parkinson disease.