[Columbine]

Glad to see someone else mention porphyria. I think it's also known as Renfield's syndrome?

There have also been a number of murderers with blood fascinations - Elisabeth Bathory, Gilles de Rais etc. though apart from modern documented cases, it is difficult to say how much of these stories is folklore.
Tuberculosis also had vampiric connections. The wasting away of sufferers attributed to vampiric attack. In some places, including I beleieve New England, those who died from consumption were exhumed by their families and laying rites such as beheading, staking, garlanding with garlic etc. may have been performed to prevent the dead from rising and preying on them. More ghoulish however was the belief that belief that to remove the deceased's heart, dry and grind into a powder/ brew which would then be consumed would be protection from them also becoming a victim of the Consumption.

As for "Sanguinarians", I'm not sorry to say they're entirely human, albeit with a heavy fetish for blood, and that IS what it is. Fetishism. Psychologically speaking anyway. You can actually more or less lump it in with cannibalism; oddly less appealing, although it's also notable that there are much fewer 'sexy' cannibals in the media. On which note, if anyone is thinking of getting into it, be very wary of hepatitis and HIV, which can be transmitted by blood drinking. And those are just two of the diseases which have been proven to do so. It's highly likely there are others, and there are definitely links between consumption of human parts (and blood IS a part, don't be fooled into thinking it's different because you can't chew it) and development of some serious diseases, some of which are resistant to both cooking AND digestion. So think carefully and don't get caught up in hyperbole. It's probably not worth it.