A condition in which tiny red or purple spots
appear on the surface of the skin
, in mucous membranes, and elsewhere owing to the escape of blood from the vessels. Purpura appears either when the capillaries become more permeable or when there is a shortage of blood platelets
which normally seal off damage
to the walls of the capillaries.
Several diseases and conditions can cause purpura. It may follow an infection such as scarlet fever; it sometimes appears in wasting diseases; and it can be caused by toxic drugs or malnutrition. In addition, the signs and symptoms occur in what is known as thrombocytopenic purpura- when there is a shortage of platelets (thrombocytopenia)- and in anaphylactoid purpura, which is thought to be associated with an allergic reaction. Henoch-Schönlein purpura is a form of allergic purpura that appears in the walls of the intestine and in the joints. It is seen most commonly in children.
The symptoms of purpura are usually feverishness and exhaustion, followed by characteristic spots on the trunk and limbs. The spots may change color from red to purple until they are nearly black; they finally disappear in much the same way as a bruise. The most serious form is purpura hemorrhagica, in which bleeding occurs from mucous surfaces in the nose and also in the mouth, digestive organs, and womb; this form may be fatal.
Thrombocytopenic purpura responds to steroid drugs, but in some cases surgical removal of the spleen (splenectomy) may be necessary. Where purpura follows infection or other disease, treatment is directed at the underlying condition.