Encyclopedia of Vampire Mythology uses the term to describe living vampires of Romanian vampire lore enough though many other vampires refer back to Living Vampire.
General Living Vampires
There are people who believe or claim to drain life energy from other living things.
Others have specific nourishment needs (other then blood) that must be met in order to live.
While a scientific reason for craving blood does exist (Hemophagia) "there is no biological means by which the human body can process raw, uncooked blood in such a way that life-sustaining nourishment can be drawn from it."
The "Vampire Disease"
Porphyria has been presented as a real life explanation for vampire legends and while it fits the characteristics of some vampires (unusually pale skin and hypersensitivity to sunlight which could cause disfigurement to exposed parts) with an old days treatment that included consuming blood, it at best only fit a very small fraction of the vampire myths.
On a practical level the enzyme in blood that could receive some symptoms doesn't survive digestion and so it would be pointless for a sufferer of the disorder to consume blood.
Never mind vampires that feed on other things besides blood: some consume a person's breath or cause them to rapidly age.
Realistically it is extremely unlikely Porphyria played a major role in the formation of any vampire myth.
Romanian vampire lore
Variants: Moroanca, Moroaica, Moroi, Mo-roii, Muroa'ica, and Strigoii Viu (“Live Vampire”)
Supernatural Living Vampires can drain life energy from from animals, crops, and people. They will gather with both living and undead vampires to teach each other black magic. When they die they come back as a undead vampire called the Strigoica.