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. Illiss 1963 paper, "On Porphyria and the Aetiology of Werewolves," 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 Dolphins paper for the American Association for the Advancement of Science, "Porphyria, Vampires, and Werewolves: The Aetiology of European Metamorphosis Legends," gained widespread media coverage, popularizing the idea.The theory has been rejected by a few folklorists and researchers as not accurately describing the characteristics of the original werewolf and vampire legends or the disease, and as potentially stigmatizing people with porphyria.A 1995 article from the Postgraduate Medical Journal (via NIH) explains:

As it was believed that the folkloric vampire could move about freely in daylight hours, as opposed to the 20th century variant, congenital erythropoietic porphyria cannot readily explain the folkloric vampire but may be an explanation of the vampire as we know it in the 20th century. In addition, the folkloric vampire, when unearthed, was always described as looking quite healthy ("as they were in life"), while due to disfiguring aspects of the disease, sufferers would not have passed the exhumation test. Individuals with congenital erythropoietic porphyria do not crave blood.
Early identification
It is recommended that patients with a history of acute porphyria, and even genetic carriers, wear an alert bracelet or other identification at all times. This is in case they develop severe symptoms, or in case of accidents where there is a potential for drug exposure, and as a result they are unable to explain their condition to healthcare professionals. Some drugs are absolutely contraindicated for patients with any form of porphyria. Neurologic and psychiatric disorders
Patients who experience frequent attacks can develop chronic neuropathic pain in extremities as well as chronic pain in the abdomen. Intestinal pseudo-obstruction, ileus, intussusception, hypoganglionosis, and encopresis in children have been associated with porphyrias. This is thought to be due to axonal nerve deterioration in affected areas of the nervous system and vagal nerve dysfunction. Pain treatment with long-acting opioids, such as morphine, is often indicated, and, in cases where seizure or neuropathy is present, gabapentin is known to improve outcome.Seizures often accompany this disease. Most seizure medications exacerbate this condition. Treatment can be problematic: barbiturates especially must be avoided. Some benzodiazepines are safe and, when used in conjunction with newer anti-seizure medications such as gabapentin, offer a possible regimen for seizure control. Gabapentin has the additional feature of aiding in the treatment of some kinds of neuropathic pain. Magnesium sulfate and bromides have also been used in porphyria seizures; however, development of status epilepticus in porphyria may not respond to magnesium alone.