For example, a molecular signature in blood composed of five genes, p19 S-phase kinase-associated protein 1A (SKP1A), huntingtin interacting protein-2 (HIP2), aldehyde dehydrogenase family 1 subfamily A1 (ALDH1A1), 19 S proteasomal protein (PSMC4) and heat shock 70-kDa protein 8 (HSPA8), distinguished early-stage and de novo PD from HC and Alzheimer’s disease patients with 90.3% sensitivity and 89.1% specificity (Molochnikov et al., 2012). The gene discussed is PSMC4; the disease is Alzheimer disease.