Figure 1 - Heme biosynthetic pathway. AIP: Acute intermittent porphyria; ALA: d-aminolevulinic acid; ALA-D: d-aminolevulinic acid dehydratase; CEP: congenital erythropoietic porphyria; COPROgen: coproporphyrinogen; CPGase: coproporphyrinogen oxidase; EPP: erythropoietic protoporphyria; Fe-Chel: ferrochelatase; HCP: hereditary coproporphyria; PBG: porphobilinogen; PBG-D: porphobilinogen deaminase; PCT: porphyria cutanea tarda; PPGase: protoporphyrinogen oxidase; PROTOgen: protoporphyrinogen; URO-D: uroporphyrinogen decarboxylase; UROgen: uroporphyrinogen; VP: variegate porphyria.