The porphyrias are a rare group of disorders secondary to haem biosynthesis dysfunction and are classified into six subsets, which are distinguished as either cutaneous porphyrias or acute porphyrias (with or without cutaneous disease) since porphyrins are toxic to tissues in high concentrations. There are three porphyrias that cause cutaneous disease only: porphyria cutanea tarda (PCT), congential erythropoietic porphyria (CEP) and erythropoietic protoporphyria. Of the porphyrias, PCT is the most common, and CEP (also called Gunthers disease) is the rarest. CEP is said to affect approximately two in every 2–3 million people. Porphyrias are autosomal dominant inherited disorders, with the exception of PCT, which can be acquired, and CEP, which is inherited in an autosomal recessive pattern.