He googleado un poco en ingles, y por lo que he visto hay argumentos en las dos direcciones. Veamos, cosas del suplemento Night's Dark Masters que da bastantes detalles sobre los vampiros.
Veamos, he encontrado un par de cosas buscando "mutation" que pueden resultar interesantes:
It is my belief that the consumption of Chaos-tainted blood or flesh has lead to greater incidences of mutation amongst some Vampires, which have then been passed on to their progeny, adding to the discrepancies between accounts.
<- esto es solo una creencia y es un texto narrativo. Por lo que puede verse como un chismorreo o considerarse como algo más cierto.
Pag 126: En la tabla de atributos aleatorios para NO muertos:
61–65 Mutant: The creature has a mutation still obvious even after death and decomposition, such as a horrible hunchback, a third eye-socket, or horns on the skull. This may just be a cosmetic effect, or you can select an appropriate mutation from WFRP, Old World Bestiary, or Tome of Corruption.
<- o sea que los no muertos aquí pone que si pueden tener mutaciones. Pero mirar al final lo que pongo en la última anotación
Luego buscando acerca de la Piedra de disformidad:
Pag 115: Debilidad a la Piedra de Disformidad:
Warpstone is particularly loathsome to these Vampires. They cannot tolerate its presence, and if they come into contact with the substance, they experience dreadful changes. A Vampire that comes within 6 yards (3 squares) of Warpstone must make a Fear Test. After each hour of contact, the Vampire must re-roll one of his weaknesses and one of his Blood Gifts.
<- vamos que sienten repulsa, aunque tampoco especifica si les afecta o no más allá del efecto psicológico.
The minions of Vlad von Carstein enter Mordheim to collect the Warpstone that fell there. Vlad plans to use the Warpstone to aid him in summoning a legion of the Undead.
The Necrarchs have discovered ways to feed their timeless existence with Warpstone or dark magic, rather than blood.
Other Necrarchs have experimented with turning themselves into mobile nexuses of dark magic, replacing the need for blood with a need for Warpstone, or recreating the Elixir of Life to Nagash’s original recipe, but all have failed
<- Vamos que está claro que los Vampiros tienen cierto contacto con la piedra de disformidad y una de dos o no pueden mutar o con tanto contacto deberían ser todos mutantes

a menos claro está que tuviesen una resistencia superior.
In addition to disease, mutation is rife amongst the peasants. The thin soil has been riddled with Warpstone since 1111, giving Sylvania one of the highest rates of mutation in the Empire.
<- quizás las mutaciones vengan, porque los muertos que alzan sean mutantes de antemano
