They are large reddish purple spots
Henoch-Schonlein pupura tends to striek children
pupura
One can find information on Purpura on health information database, From pupura support group like National Heart, Lung and Blood Institute ,National Institute of Diabetes and Digestive and Kidney Disease and health information centres.
A bruise is broken blood vessels under the skin that causes the area to take on a dark appearance. Bruises, or ecchymoses, are a discoloration and tenderness of the skin or mucous membranes due to the leakage of blood from an injured blood vessel into the tissues. Pupura refers to bruising as the result of a disease condition. A very small bruise is called a petechia. These often appear as many tiny red dots clustered together, and could indicate a serious problem. (Taken from yahooanswers definitions I didn't write this)