DefinitionPorphyrias are a group of rare disorders passed down through families, in which an important part of hemoglobin, called heme, is not made properly. Heme is also found in myoglobin, a protein found in certain muscles.Alternative NamesAcute intermittent porphyria; Hereditary coproporphyria; Congenital erythropoietic porphyria; Erythropoietic protoporphyriaCauses, incidence, and risk factorsNormally, the body makes heme in a multi-step process. Porphyrins are made during several steps of this process. Patients with poryphyria have a lack (deficiency) of certain enzymes needed for this process. This causes abnormal amounts of porphyrins (or related chemicals) to build up in the body.There are many different forms of porphyria. The most common type is porphyria cutanea tarda (PCT).Dru