PSEN2 and metachromatic leukodystrophy: For instance, among genetic mutations linked to known hNDDs, examples include HTT gene mutation in HD [47], SOD1 in amyotrophic lateral sclerosis [48], PSEN1, PSEN2, and APP in AD [49], ARSA gene mutation in metachromatic leukodystrophy (MLD) [50], and others.