Since the most relevant quantitative differences among both CLN2 and CLN3 fibroblasts are in TPP1 activity (fully lost in CLN2 and only partially in CLN3 fibroblasts) and the increased generation of ROS (larger in CLN2 fibroblasts), and both are known to contribute to the accumulation of lipofuscin, these differences could account for the higher severity of LINCL over JNCL. This evidence concerns the gene TPP1 and juvenile neuronal ceroid lipofuscinosis.