The cytochrome genes that were found to undergo significant epigenetic alterations in AD and that are related to these pathways were the following: CYP1A1, CYP2A7, CYP2A13, CYP2C9, CYP2D6, CYP2J2, CYP2S1, CYP3A43, CYP4A22, CYP4B1, CYP4Z1, CYP11A1, CYP11B2, CYP19A1, and CYP21A2. The gene discussed is CYP21A2; the disease is Alzheimer disease.