Though evidence has showed that several genes including multiple major histocompatibility complex (MHC)-related genes, AIRE (autoimmunity regulator) and CYP2D6 (hepatocyte enzyme) are associated with AIH risk [17], but the mechanistic details regarding the development and pathogenesis of AIH are complex and remain to be fully elucidated. The gene discussed is CYP2D6; the disease is autoimmune hepatitis.