CTSD and neuronal ceroid lipofuscinosis: To date, about 500 mutations (https://www.ucl.ac.uk/ncl-disease/mutation-and-patient-database/mutation-and-patient-datasheets-human-ncl-genes; accessed on 21 March 2021) in 13 different genes have been shown to cause different NCL forms (CLN1-8 and CLN10-CLN14) [7,8].