PDGFRA and Alzheimer disease: The expression of several genes linked to the oligodendrocyte lineage was reduced at stages III–IV/0–C when compared with MA and with AD stages I–II/0‐A including OLIG1 (P = 0.007, when compared with ADI–II/A–C) and PDGFRA (P = 0.000 when compared with MA, and P = 0.029 when compared with ADI–II/0‐A).