In the 1980’s, some historians claimed that the vampire myth may have come about because of a little known genetic condition called PORPHYRIA.
But is this really the case? In some ways it makes a lot sense that people thought vampires originated because of porphyria. The condition symptoms include high sensitivity to light, recessed gums and tightening around the lips so that the teeth appear larger, and in some more extreme cases, violent psychotic episodes. Plus, one of the treatments for porphyria in the Middle Ages was the drinking of blood. Sounds a lot like our modern vampire.
But, today, we know that the vampire myth is actually not tired this genetic condition. In fact, the archetypal vampire was quite different from our modern conception. Early vampires could go out in the sun for example. And we know that the vampire myth was largely based on how the human body looks as it decomposes. Exhumed bodies often look plump and life like which tricked people into thinking they weren’t dead, hence the vampire myth.
Also, while people with porphyria experience a range of symptoms, none crave blood. Still the vampire myth is one of many problems that they have to deal with in their everyday lives. Because some medical professionals are not well versed in porphyria, the condition sometime goes undiagnosed and untreated for years.
So basically, Vampire is just a myth of old times or we say a mistake by the the people to understand the problem of porphyria.
Source : Seeker Network