TPP1 and late infantile neuronal ceroid lipofuscinosis: CNL2 also known as “Late Infantile Neuronal Ceroid Lipofuscinosis (LINCL),” derives from a defect in the lysosomal gene CLN2 encoding the enzyme tripeptidyl peptidase 1 (TPP1) (Kohlschütter and Schulz, 2016), resulting in the lysosomal accumulation of ceroid lipofuscin.