Most cultures have superstitions involving beings more or less similar to what we call vampires. In this post I intend to offer a possible medical explanation for these creatures. A condition known as Porferia is caused by a malformation of an enzyme in haem. Haem is a crucial element in our blood and allows our red blood cells to bind to oxygen. The condition can easily be fatal without a treatment, a suppliment of artifical haem. Lets break down the "signs" of vampirism.
The folklore states that vampires need to drink blood in order to survive. This is technically a solution for porferia suffers, Ingesting large amounts of human blood would provide the required elements to suppliment low haem levels. However most of the ingested blood would be immediately broken down and unusable in the stomach.
Sensitivity to Sunlight
Three types of porphyria are associated with a sensitivity to light, which can be as extreme as sever sunburn at minor exposure. Most sunscreens are totally non-effective.
Most legends suggest that vampires are very pale in complexion. Maybe because the legends state they dont get out much during the day? Most people suffering from porpyria are very pale in complexion as a result of barely functioning red blood cells.
Despite all this there are a few bits where the legends dont match up to the medical condition. As far as medical science is aware porphyria suffers cant fly. Also the legends all seem to give vampires a far eastern european accent. Porphyria is one of surprisingly few condtions that dont seem to effect any ethnic group more or less.
This connection has been suggested in the past by many academics one of the better works was a paper writen by a biochemist named David Dolphin in 1985. These suggestions are deeply contravercial as it adds an additional stigma unto suffers of what is in reality a very natural and saddening condition.