A group of metabolic diseases due to deficiency of one of a number of liver enzymes in the biosynthetic pathway of heme. They are characterized by the accumulation and increased excretion of porphyrins or its precursors. Clinical features include neurological symptoms (porphyria, acute intermittent), cutaneous lesions due to photosensitivity (porphyria cutanea tarda), or both (hereditary coproporphyria). Hepatic porphyrias can be hereditary or acquired as a result of toxicity to the hepatic tissues.