Purpura (from the Latin, purpura, meaning "purple") is the appearance of red or purple discolorations on the skin, caused by bleeding underneath the skin. Purpura measure 0.3-1cm, while petechiae measure less than 3mm, and ecchymoses greater than 1cm.
There are also cases of psychogenic purpura described in the medical literature, some claimed to be due to "autoerythrocyte sensitization." Other studies suggest, that local (cutaneous) activity of tPA can be increased in psychogenic purpura, leading to substantial amounts of localized plasmin activity, rapid degradation of fibrin clots, and resultant bleeding. Petechial rash is also characteristic of a rickettsial infection.