Vampires and werewolves:
Porphyria has been suggested as an explanation for the origin of vampire and werewolf legends, based upon certain perceived similarities between the condition and the folklore.
In January 1964, L. Illis' 1963 paper, "On Porphyria and the Aetiology of Werwolves", was published in Proceedings of the Royal Society of Medicine.
Later, Nancy Garden argued for a connection between porphyria and the vampire belief in her 1973 book, Vampires. In 1985, biochemist David Dolphin's paper for the American Association for the Advancement of Science, "Porphyria, Vampires, and Werewolves: The Aetiology of European Metamorphosis Legends", gained widespread media coverage, thus popularizing the connection.
The theory has since faced criticism, especially for the stigma it has placed on its sufferers. Norine Dresser's 1989 book American Vampires: Fans, Victims, Practitioners deals with this.
The theory also operates on a flawed premise, mainly in regard to a perceived harmful effect sunlight had on vampires, a property relatively late to vampire belief.
There are about eight different types of porphyria; four of these can sometimes cause sensitivity to light: Erythropoietic Protoporphyria (EPP) or Protoporphyria, Congenital Erythropoietic Porphyria (C.E.P.), Porphyria Cutanea Tarda (PCT) and Variegate Porphyria.