The blood disorder that inspired vampire lore
Like many myths, the myth of vampires is based partly in fact.

The concept of a vampire predates Bram Stoker’s tales of Count Dracula – probably by several centuries. But did vampires ever really exist?
In 1819, 80 years before the publication of Dracula, John Polidori, an Anglo-Italian physician, published a novel called The Vampire. Stoker’s novel, however, became the benchmark for our descriptions of vampires. But how and where did this concept develop? It appears that the folklore surrounding the vampire phenomenon originated in that Balkan area where Stoker located his tale of Count Dracula.
Stoker never travelled to Transylvania or any other part of Eastern Europe. (The lands held by the fictional count would be in modern-day Romania and Hungary.)
The writer was born and brought up in Dublin. He was a friend to Oscar Wilde and William Gladstone. He was both a Liberal and a home-ruler – in favour of home rule for Ireland. He turned to theatre, and became business manager of the Lyceum Theatre in London. It was his friendship with Armin Vambery, a Hungarian writer, that led to his fascination with vampire folklore. He consulted Vambery in the writing of Dracula, whose main character was loosely fashioned on Vlad the Impaler, a bloodthirsty prince born in Transylvania in 1431.
Medical source of the myth
But where did the myth of...