Beyond AD and PD, age-related declines in Klotho8,13,17,24,53 are associated with a range of other deteriorating central nervous system (CNS) processes.17,24 For example, mounting evidence implicates dysregulation of Klotho in shared mechanistic pathological relationships linking iron and myelin in various common and rare brain diseases,54–56 including abnormalities in myelination and the maturation of oligodendrocytes that are central to the pathogenicity of diseases such as multiple sclerosis (MS)26,56,57 and amyotrophic lateral sclerosis (ALS).56,58. Here, KL is linked to Parkinson disease.