Not all of those who identify themselves with vampires are mentally ill or have a personality disorder. Some people who adopt a vampire persona use it as a means to manifest violence against others.
Diagnosed clinical vampirism is different than someone with a violent sexual fetish, acting out in a vampiric manner. Those who have clinical vampirism exercise somewhat rational control.
Many psychiatrists and psychologists have written about vampiric symptoms.
Clinical vampirism is more of a craving for the blood of others versus a gratification from receiving the blood. Those who are classified as a clinical vampire suffer the delusions of being a real vampire.
Renfield’s Syndrome is the psychiatric name for Clinical Vampirism.