Purpura

Author: Vanessa Ngan, Staff Writer, 2005. Updated by Hon A/Prof Amanda Oakley, November 2015.

What is purpura?

Purpura is the name given to the discolouration of the skin or mucous membranes due to haemorrhage from small blood vessels.

Petechiae are small, purpuric lesions up to 2mm across
Ecchymoses or bruises are larger extravasations of blood.
Palpable purpura is purpura than can be felt, due to inflammation of the blood vessels (vasculitis)
Pigmented purpura is a sign of petechial haemorrhages associated with capillaritis

Extravasated blood usually breaks down and changes colour over a few weeks from purple, orange, brown and even blue and green.

There are many different types of purpura. Their classification depends on the appearance or cause of the condition.

Platelet disorders	Thrombocytopaenic purpura—due to destruction of platelets Primary (idiopathic) thrombocytopaenic purpura due to autoimmune or unknown reasons Secondary thrombocytopaenic purpura due to external or internal factors such as drugs, infections, systemic diseases
Other coagulation disorders	Disseminated intravascular coagulation – clinical picture varies from a severe and rapidly fatal disorder (purpura fulminans) to a relatively minor disorder Heparin-induced thrombocytopenia – purpura and necrosis due to anti-platelet antibodies inducing platelet plugs that block blood vessels Warfarin-induced necrosis – purpura and necrosis due to blood clots related to relative protein C deficiency early in treatment
Vascular disorders	Non-thrombocytopaenic purpura—leakage of blood through the vessel wall Damage to small blood vessels Increase in intraluminar pressure Deficient vascular support, as in aged or sun damaged skin (senile purpura)

The signs and symptoms of purpura vary according to the type of purpura. The following broad generalisations may be made.

Petechiae are usually present in thrombocytopaenic purpura. There may be some external bleeding and bruising.
Coagulation defects usually present as large ecchymoses and external bleeding. Petechiae do not feature.
Inflamed blood vessels (vasculitis) cause persistent and localised purpura with an erythematous inflammatory component. This may be palpable. Ecchymoses and external bleeding are uncommon.