PCT, the most common type of porphyria, is in most cases (type I) an acquired deficiency of Uroporphyrinogen decarboxylase (UROD), the fifth enzyme in heme biosynthesis, caused by underlying liver diseases triggered by alcohol, iron overload, chlorinated hydrocarbons, oestrogens or viral hepatitis (Frank and Poblete-Gutierrez, 2010). The gene discussed is UROD; the disease is animal viral hepatitis.