Late infantile neuronal ceroid lipofuscinosis (LINCL), a subclass of NCL with an onset age of 2 to 4 years (Schulz et al., 2013), is caused primarily by mutations in the lysosomal peptidase tripeptidyl peptidase 1, or TPP1 (Sleat et al., 1997). The gene discussed is TPP1; the disease is late infantile neuronal ceroid lipofuscinosis.