AIH is characterized by a portal mononuclear cell infiltration of the liver parenchyma that is associated with presence of ANAs and/or smooth muscle (AIH type 1) or anti-liver kidney microsomal or anti-liver cytosol type 1 autoantibodies, which target the microsomal cytochrome CYP2D6 or FTCD, respectively (AIH Type 2)18. The gene discussed is CYP2D6; the disease is autoimmune hepatitis.