TPP1 and lysosomal storage disease: In addition, CSF and blood Nf-L levels have been shown to be responsive to disease-modifying treatment in relapsing forms of MS [24], spinal muscular atrophy [25], and lysosomal storage disorders such as neuronal ceroid lipofuscinosis type 2 (CLN2) [26], suggesting it is possible to monitor treatment effects on neurodegeneration in peripheral biofluids.