TPP1 and neuronal ceroid lipofuscinosis: To date, 13 autosomal recessive and one autosomal dominant gene have been associated with NCL, including both secreted lysosomal protein-coding genes (CLN1, CLN2, CLN5, CLN10 and CLN13) and transmembrane protein-coding genes (CLN3, CLN4, CLN6, CLN7, CLN8, CLN12 and CLN14) [6].