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 span for several minutes or for many hours or days.

In acute cases, a subject who is suffering from a cataleptic episode will seem dead. Indications of life can solely be detected by means of modern medical instruments. Medieval patients with catalepsy might have been laid to rest while still alive. Later, when they recaptured their muscular control they most certainly would have attempted to free themselves from their grave site. Some vampire legends describe banging coming from freshly buried coffins. After local townspeople exhumed these graves and opened them, claw marks were discovered on the lining, leading townspeople to deduce that vampires were trying to free themselves from their graves.

Anemia is a malady distinguished by the blood not having enough healthy red blood cells. Because red blood cells carry oxygen all over the body, symptoms encompass weakness, vertigo, loss of appetite, and fatigue. These maladies are a result of the body's organs not receiving enough oxygen. These symptoms also approximate the symptoms of vampire victims in traditional folklore. Anemia is a widely occurring disease.

Wolves and Bats are both often associated with vampires. They are common carriers of the disease rabies. Rabies has characteristics that are similar to vampirism. Hyper-sensitivity, a symptom of rabies, could result in garlic or light allergy. Other characteristics include becoming nocturnal due to unusual sleep patterns and over-sexuality. The disease is passed on by biting, and persons with this disease are sometimes seen frothing with blood at the mouth.

Modern medical science can clarify some of history's early vampire folklore. Anemia, catalepsy, porphyria, and rabies are all feasible reasons for historic vampire legends. Persons of the time who lacked medical knowledge would not know of these conditions and their symptoms. The result might be the vampire tales that spread throughout Europe in the middle ages.