Perusing YouTube for "real vampire" comes up with close to a dozen different variations. The three major "species" seem to be "sangs", i.e., sanguinary vampires that drink blood, psychic vampires that drink life force, and lifestylers who like a look that is somewhere beyond gothic. All three groups sometimes have fangs and sometimes do not.
In psychology and criminology, "vampire" is a term informally used to refer to psychopaths or narcissists in various contexts. On one end of the spectrum, it concerns the habit of such people to leave long-term friends and family emotionally drained, due to years of subtle- or not so subtle- psychological or physical abuse, and to their needs for attention, adoration, fear, or control. At the other, it sometimes refers to serial killers.
Cutaneous porphyria is a genetic disorder that causes photosensitivity, blisters, and necrosis of the skin. In folklore it has been presented as the cause of werewolves and vampires, while its real world sufferers received misplaced criticism and stigma.
Renfield Syndrome is a mental illness whereby the patient believes they are a vampire, or that they are becoming one. They usually suffer from schizophrenia and it tends to be a symptom, meaning that proper treatment can put the delusion under control.
Named after a character suffering from a similar condition from the novel Dracula.
Hematophagy is the practice of some animals that feed on blood for their diets.
The scientific name for the blood-thinner in their saliva is called "draculin."
Several kinds of internal parasite.
Butterflies may do this.
UK Member of Parliament Peter Mandelson is often nicknamed "The Vampire" for his rather unnatural air and manner.