Animal models with a disrupted hemochromatosis gene (Hfe −/−) and a disruption of one of the Urod alleles developed uroporphyria, which is the equivalent of human PCT in mice, whereas Urod −/+ mice were not affected [70,71], reinforcing the concept of an iron-driven second hit. The gene discussed is UROD; the disease is porphyria cutanea tarda.