The genotyping studies of CYP2C19*, CYP2D6* and CYP3A5* resulted in the exclusion of the patient samples, who were genetically determined with the enzyme deficiency, i.e., for CYP2C19—2 controls, and for CYP2D6—1 control as well as AIH—1, HCV—1 and PBC—1 sample. The gene discussed is CYP2C19; the disease is autoimmune hepatitis.