I apologize if there is already a thread about this. I did not find it. However I was wondering if your Skyrim character has Vampirism will that affect being able to become a Vampire Lord in Dawnguard? In other words are the two treated differently? one as a desease and the other as a race?
As it's displayed in game, Vampirism starts off as a disease (Sanguinare Vampiris), but after three days it changes to full Vampirism and your race changes to Vampire. In game, you are treated as Undead (evidenced by the perk called "Necromage", that boosts any spell effects you cast on Undead, which include yourself).
Having regular Vampirism isn't a disease; it can't be cleansed by cure disease, and the game changes your race to Vampire (NPCs stop recognizing you as a Nord, for example. Guards won't say "What can I do for a fellow Nord?" or "Greetings, kinsman".)
Being a Vampire -Lord- however, means you're part of a bloodline that is closer to the source of where the Vampire race comes from. It means your blood is purer than a regular Vampires. Your race in game is still registered as Vampire, however. It's just you have more powers, and are part of an elite family.