The Auspitz sign is simply bleeding that occurs after psoriasis scales have been removed. It occurs because the capillaries run very close to the surface of the skin under a psoriasis lesion, and removing the scale essentially pulls the tops off the capillaries, causing bleeding. Auspitz sign is also found in other scaling disorders such as Darier's disease and actinic keratoses.
Sources:
Bernhard JD. "Auspitz sign is not sensitive or specific for psoriasis." Journal of the American Academy of Dermatology. 6(1990):1079-81.
Bernhard, Jeffrey. "Clinical Pearl: Auspitz sign in psoriasis scale." Journal of the American Academy of Dermatology. 36(1997):621.
Habif, Thomas. "Psoriasis." Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 209-39.
van de Kerkhof, Peter. "Psoriasis." Dermatology. Ed. Jean Bolognia. New York: Mosby, 2003: 531-5. 125-37.
