Erythropoietic porphyria is a defect of porphyrin metabolism of blood-producing tissues.
Hepatic porphyria is a defect in porphyrin metabolism of the liver. The symptoms of porphyria cannot be completely explained by our current understanding of the biochemical defect. In all cases there is an identifiable abnormality of the enzymes which synthesize heme. This leads to accumulation of intermediates of the pathway and a deficiency of heme . Accumulation of porphyrinogens in the skin can lead to photosensitivity .