Consistent with this, neither APEH mRNA nor two metabolically related genes, NAA10 and ACY1, showed changes between PD and HLT, thus suggesting that, despite shared neurodegenerative features, peripheral APEH dysregulation is not a common biomarker across PD and AD and is unlikely to be centrally involved in peripheral proteostatic dysfunction in PD. This evidence concerns the gene APEH and Parkinson disease.