No they are not. however psychic vampires do exist. to add some intellectual speculation porphyria is a recognized legit desease(genetic) that makes the skin sensitive to light and occasionally makes the teeth jut up("fangs"). Heme,a blood product, is said to be a treatment.
By: Lark Moderator / Knowledgeable Jan 30, 2013
Post # 5
Porphyria can make the skin sensitve to sunlight and it causes various sorts of anemias because hemoglobin is not produced properly. However, it does not cause your teeth to grow into fangs or even to become sharper.
Treatment for porphyria does not require blood transfusions unless the patient becomes extremely anemic. And of course in these cases the blood must be given intravenously. Blood ingested by mouth is simply digested and never effects the hemoglobin levels at all.