N eurodegeneration occurs in the majority of the more than 40 known lysosomal storage diseases. Since the nervous system in these disorders can be globally affected, effective treatment would require persistent widespread correction. Biffi et al. show such correction is possible in a mouse model of metachromatic leukodystrophy by the transplantation of hematopoietic cells genetically modified to overexpress the missing lysosomal enzyme. The results reveal a nervous system damage-response pathway that can be harnessed to provide therapy to the nervous system in these serious disorders.