The secondary NEU1 deficiency occurred in the brains of all analyzed mouse models of neurological MPS (MPS I, II, IIIA, IIIB, IIIC) but not in the models of other LSDs (metachromatic leukodystrophy, ML IV, Tay-Sachs, or NPC1). Here, NPC1 is linked to metachromatic leukodystrophy.