OverviewInflammation of the blood vessels (vasculitis) may be caused when antibodies that have attached to antigens in the blood (immune complexes), attach to the blood vessel walls. These purplish spots can be felt in the skin. They do not turn white (blanch) when pressed. As the condition progresses, they may become larger and more bruise-like (ecchymotic), and some may develop central ulceration or necrosis (tissue death).
Update Date 4/28/2015
Updated by: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.