Allergic Purpura
A nonthrombocytopenic purpura, allergic purpura is an acute or chronic vascular inflammation that affects the skin, joints, and GI and genitourinary (GU) tracts in association with allergy symptoms. When allergic purpura primarily affects the GI tract with accompanying joint pain, it’s called Henoch-Schönlein syndrome or anaphylactoid purpura. However, the term allergic purpura applies to purpura associated with many other conditions such as erythema nodosum. An acute attack of allergic purpura can last for several weeks.
Fully developed allergic purpura is persistent and debilitating. This disorder affects males more commonly than females and is most prevalent in children ages 3 to 7. The prognosis is more favorable for children than for adults. The course of Henoch-Schönlein syndrome is usually benign and self-limiting, lasting 1 to 6 weeks if renal involvement isn’t severe.
Causes
The most common identifiable cause of allergic purpura is probably an autoimmune reaction directed against vascular walls and triggered by a bacterial infection (particularly a streptococcal infection such as scarlet fever). Typically, upper respiratory tract infection occurs 1 to 3 weeks before the onset of signs and symptoms. Other possible causes include allergic reactions to some drugs and vaccines, allergic reactions to insect bites, and allergic reactions to some foods (such as wheat, eggs, milk, and chocolate).
Complications
Assessment
An accurate patient allergy history may yield information that helps ensure a positive outcome. The patient history may include pain and bleeding due to bleeding from the mucosal surfaces of the ureters, bladder, and urethra. In 25% to 50% of patients, allergic purpura is associated with GU symptoms. Other patient complaints include moderate, transient headaches; fever; anorexia; edema of the hands, feet, or scalp; and skin lesions, accompanied by pruritus, paresthesia and, occasionally, angioneurotic edema.
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