In patients with Gaucher disease, ceroid lipofuscinosis type 1 (CLN1), Niemann–Pick disease type C and A, Krabbe and Pompe diseases, gangliosidosis GM2 and metachromatic leukodystrophy discreet or no changes in DPP-IV activity were observed. Here, DPP4 is linked to metachromatic leukodystrophy.