Haematoma is a localised collection of blood, usually clotted, in an organ, space or tissue, due to a break in the wall of a blood vessel. It may be classified according to the degree affected. It may be petechiae, purpura, or ecchymosis.
Purpura is a small haematoma that ranges from 3 to 10 mm in diameter. It is reddish or purplish in colour (thus, the name). It does not blanch when pressure is applied. It may be caused by various factors, e.g. blood disorders, vascular abnormalities and trauma.
Purpura is common in certain diseases such as typhus and meningitis. Purpura may also be associated with disorders, such as platelet disorders (thrombocytopenic purpura), vascular disorders (nonthrombocytopenic purpura), and coagulation disorders (e.g. disseminated intravascular coagulation and scurvy).