Purpura

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.

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

Classification of purpura

There are many different types of purpura and their classification in medical literature, depending on the appearance or cause of the condition. Often there is overlap and difficulty in classifying any individual case of purpura. The following table is one way of classifying purpura according to the underlying cause.

Platelet disorders	Thrombocytopaenic purpura Primary (idiopathic) thrombocytopaenic purpura – destruction of platelets due to unknown cause Secondary thrombocytopaenic purpura – caused by external or internal factors, e.g. drugs, infections, certain diseases
Vascular disorders	Non-thrombocytopaenic purpura – blood may leak as a result of: Damage to small blood vessels Increase in the intraluminar pressure Deficient vascular support, as in aged or sun damaged skin (senile purpura)
Coagulation disorders	Disseminated intravascular coagulation – clinical picture varies from a severe and rapidly fatal disorder (purpura fulminans) to a relatively minor disorder

What are the signs and symptoms of purpura?

The signs and symptoms of purpura vary depending on 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.
Lesions of blood vessels cause persistent and localised purpura with an erythematous inflammatory component. This may be palpable. Ecchymoses and external bleeding are uncommon.