Purpura
Purpura is the name given to a rash caused by bleeding from capillaries into the skin. The spots may be small, like pin-heads, or large and blotchy. Unlike the spots caused by dilated blood vessels, they don't fade when pressed by a glass (because they are caused by blood in the skin). There are different causes involving a decrease in the number of platelets, responsible for blood clotting, in the circulation - a condition called thrombocytopenia - which can be secondary to drug treatment or as a result of autoimmune attack on the platelets. In the presence of a normal number of platelets the bleeding can be caused by damage to the vessels - this is the mechanism whereby meningococcal septicaemia produces its rash.
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