porphyria
This rare disease known as the "vampire" or "Dracula" disease, or by it's proper medical name, porphyria (pronounced por-fer-e-ah, or por-fi-re-ah) is thought to be one of, or the reason for the vampire scares throughout time, in cultures around the world. It is very hard to describe it out of a nurse's dictionary-- it's a lot on the technical side-- but I'm going to try my best to put it in layman's terms.
First of all, porphyria is a genetic disease. Because it is hereditary, it can't be caught by blood or other fluid exchange. There shoots down all those old legends of vampires biting someone and they become a vampire themselves. If having porphyria makes you a vampire, then you cannot give it to others. You cannot make other vampires. You cannot "embrace" anyone. I'm not sure to what percent it is that it gets passed from parent to child, i.e. I'm not sure if 100% of children of a porphyritic (making up a word here) parent gets it or if 50% of them do, or if it passes more readily into one sex or another or if grandchildren are more likely to get it than children (as is sometimes the case with hereditary diabetes). The only sure thing is you can't get it through blood or bodily fluid transfer. Sorry if that ruins your evening plans of a little... necking.
Porphyrins (hence the lack of them gives you the name of the disease), combined with iron form hemes in the blood. Heme is what makes blood red. If you don't have the right porphyrin content, you don't have the right heme contents, and then things start to go bad. Prophyria imbalance can cause the following:
gastrological problems (stomach cramping, nausea)
neurological and psychological disorders (you get crazy)
photosensitivity (intolerance to sun or bright lights)
pigmentation of the face (skin changes color, usually getting lighter, losing color)
anemia (blood deficiency) with enlargement of the spleen (an organ acting as a reservoir for blood)
and excessive amounts of porphyrins are excreted in the stool and urine, giving it a dark red, bloodish color.
If you look at all the symptoms of porphyria, you can begin to see how it could start looking like what we know as a vampire. Mentally unstable people, perhaps snarling, flashing their teeth. Perhaps biting others. Some people report that porphyria is helped by giving blood, IV. Back before such things, you might find people suffering of the disease drinking blood to help them feel better. They are photosensitive, their skin, in extreme cases, prone to blistering and burning in the sunlight, so they would have a preference to avoid it. Discoloration of the skin or loss of pigmentation, coupled with a low amount of blood, would give suffers a very pale appearance indeed. But before you say "Aha!" and pronounce this as the truth behind the vampire scares, be advised, this is a very rare disease. There are several classifications of it as well, not all of them having all of the symptoms. Those symptoms closest to being "vampire related" appear only in a handful of cases. As of 1991, there were only 60 reported cases of the form of porphyria, CEP, that has symptoms most commonly linked with vampirism.1
