Hemophilic, allergic to sunlight (extreme photosensitvity), allergic to some of the lighter heavy metals - such as silver (argentophobia).
Vampires should develop deformities such as elongated cuspid teeth, extreme lack of body fat, accelerated hair and nail growth, loss of skin saturation, discoloration of irises, and an agressive attitude.
Other than that, the Porphyric hemophilia should grant vampires some superhuman abilities - increased strength, agility, night vision (Tapetum lucidum), and the ability to survive on human blood. ^^
Damn, I like using Wikipedia and finding all those nice definitions.