Further, defective proteolytic events by cathepsins can lead to several LSDs, namely, galactosialidosis [63] neuronal ceroid lipofuscinosis (CLN) type 10 and 13 [63,64], Papillon–Lefèvre syndrome [65], pycnodysostosis [66], and Alzheimer’s disease [21]. The gene discussed is CTSS; the disease is infantile neuronal ceroid lipofuscinosis.