Vampire myths are widespread throughout medieval history. Some stories date back as far as the 12th century. It's possible that these early stories of vampires were created by real medical circumstances.
There are numerous classifications of porphyria. Four of the classifications have symptoms of sunlight aversion: Porphyria Cutanea Tarda (PCT), Protoporphyria or Erythropoietic Protoporphyria (EPP), Variegate Porphyria, and Congenital Erythropoetic Porphyria (C.E.P.). Additional symptoms include hypertrichosis (excessive hair growth), red and sometimes bloody gums, and brown teeth. These symptoms mirror many vampire tales. Still, victims of porphyria don't desire or consume blood.
Catalepsy is a tactile malady defined by a decreased sensitivity to stimuli in addition to muscular rigidity. Subjects with catalepsy don't respond to outside stimuli. They are aware of their environment but they can't speak or move. Episodes of catalepsy may last for a few minutes or for a few days.
In severe cases, a patient that is enduring a cataleptic attack will appear to be dead. Signs of life can only be identified by way of scientific medical equipment. Ancient sufferers of catalepsy could have been buried alive. Some time later, when patients regained muscular control patients most definitely would've attempted to escape from their coffins. Some vampire tales describe noises coming from newly buried coffins. Later, when local villagers dug up these graves and unlocked them, scoring marks were discovered on the interior, leading townspeople to conclude vampires were attempting to escape from their coffins.
Anemia is a condition characterized by blood that doesn't have adequate red blood cells. Since red blood cells transfer oxygen all around the body, symptoms include fatigue, weakness, loss of appetite, and vertigo. These symptoms are a result of the body's organs not obtaining sufficient oxygen. These symptoms also resemble the symptoms of vampire victims in early legends. Anemia is a very common condition.
Bats and Wolves both are oftentimes connected with vampires. They are common carriers of the disease rabies. This disease has symptoms that resemble vampirism. Hyper-sensitivity, a characteristic of rabies, might result in light or garlic repulsion. Other symptoms entail becoming nocturnal due to aberrant sleep patterns and hyper-sexuality. Rabies is spread by biting, and patients with rabies are oftentimes observed frothing at the mouth with blood.
Today's medical science may translate some of Europe's medieval vampire myths. Porphyria, catalepsy, anemia, and rabies are all explainable causes of early vampire myths. Villagers of the period who were short on medical education wouldn't comprehend these diseases and their symptoms. The result could be the vampire legends that ran rampant in Europe in the middle ages.