There are many "symptoms" alleged to be related to being a vampyre, but most appear pretentious.
A vampyre is a person following one of the paths found in Satanism. One of the better noted is seeing Lilith as a deity of worship as she has been labeled by some as being a Vampyre.Some alleged heightened senses, but people with heightened senses can be found all over the occult spectrum. Many state Vamps have darker auras which is probable given they are draw to deities and demons labeled dark. One of the noted theories is that they require energy, although this could just be a stereotype given they tend to take energy from others. There is a theory in the atheistic area that Vamps are simply drama queen type people, although I believe the path has evolved much since the theory initially cam out.
There is a website called awake and drink that seems to separate fact from fake regarding those Practitioners following the real path and those that pretend. I haven't read the site in it's entirety, so I could be wrong, but from what I had read on one page, the person that owns the site appears down to earth and non pretentious.