A type of nonthrombocytopenic purpura, allergic purpura is an acute or chronic vascular inflammation affecting the skin, joints and GI and geniurinary (GU) tracts in association with allergy symptoms. When allergic purpura primarily affects the gastro-intestinal (GI) tract, with accompanying joint pain, it is called Schoenlein-Henoch 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 and is potentially fatal (usually from kidney failure); however, most people do recover.
Fully developed allergic purpura is persistant and debilitating, possibly leading to chronic glomerulonephritis (especially following a streptococcal infection). Allergic purpura affects more males than females and is most prevalent in children ages 3 to 7 years. The prognosis is more favorable for children than adults.
CAUSES
The most common cause of allergic purpura is an autoimmune reaction directed against vascular walls, triggered by a bacterial infection. Typically, upper respiratory infection occurs 1 to 3 weeks before the onset of symptoms. Other possible causes include allergic reactions to some drugs and vaccines, insect bites and some foods (such as wheat, eggs, milk and chocolate).
SIGNS & SYMPTOMS
Allergic purpura produces characteristic purple skin lesions which are caused by vascular leakage into the skin and mucous membranes. The lesions usually appear in symmetrical patterns on the arms and legs and are accompanied by itchiness, burning and tingling sensation and swelling.
Schoenlein-Henoch syndrome commonly produces transient or severe colic, constipation, vomiting, swelling and bleeding of the mucous membranes of the bowel, resulting in GI bleeding, blood in stools, and telescoping of one loop of the intestine into another. Such GI abnormalities may precede overt, skin symptoms of purpura. Musculoskeletal symptoms, such as rheumatoid pains most commonly affect legs and feet.
Also possible are moderate and irregular fever, headache, loss of appetite, swelling of the hands, feet and scalp.
TREATMENT
In allergic purpura, treatment is generally aimed at relieving symptoms; for example, severe allergic purpura may require steroids to relieve swelling and analgesics to relieve joint and abdominal pain. Some individuals with chronic kidney disease may need immunosuppressive medications, along with identification of the provocative allergen.
After the acute stage, tell your doctor of any recurrence of symptoms (recurrence is most common about 6 weeks after initial onset) and return for follow-up urinalysis.