Allergic purpuras
Allergic purpura, a nonthrombocytopenic purpura, is an acute or chronic vascular inflammation affecting 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 and is potentially fatal (usually from renal failure); however, most patients do recover.
Fully developed allergic purpura is persistent and debilitating, possibly leading to chronic glomerulonephritis (especially following a streptococcal infection).
Causes and incidence
The most common identifiable cause of allergic purpura is probably an autoimmune reaction directed against vascular walls, triggered by a bacterial infection (particularly streptococcal infection). Typically, upper respiratory tract infection occurs 1 to 3 weeks before the onset of symptoms. Other possible causes include allergic reactions to some drugs and vaccines, to insect bites, and to some foods (such as wheat, eggs, milk, and chocolate).
Allergic purpura affects more males than females and is most prevalent in children ages 3 to 7. The prognosis is more favorable for children than adults.
Signs and symptoms
Characteristic skin lesions of allergic purpura are purple, macular, ecchymotic, and of varying size. They’re caused by vascular leakage into the skin and mucous membranes. (See Purpuric lesions.) The lesions usually appear in symmetric patterns on the arms, legs, and buttocks and are accompanied by pruritus, paresthesia and, occasionally, angioneurotic edema. In children, skin lesions are generally urticarial and expand and become hemorrhagic. Scattered petechiae may appear on the legs, buttocks, and perineum.
Henoch-Schönlein syndrome commonly produces transient or severe colic, tenesmus (spasmodic contraction of the anal sphincter) and constipation, vomiting, and edema or hemorrhage of the mucous membranes of the bowel, resulting in GI bleeding, occult blood in the stool and, possibly, intussusception. Such GI abnormalities may precede overt, cutaneous signs of purpura. Musculoskeletal symptoms, such as rheumatoid pains and periarticular effusions, mostly affect the legs and feet.
In 25% to 50% of patients, allergic purpura is associated with GU signs and symptoms: nephritis; renal hemorrhages that may cause microscopic hematuria and disturb renal function; bleeding from the mucosal surfaces of the ureters, bladder, or urethra; and, occasionally, glomerulonephritis. Also possible are moderate and irregular fever, headache, anorexia, and localized edema of the hands, feet, or scalp.
Diagnosis
No laboratory test clearly identifies allergic purpura (although white blood cell count and erythrocyte sedimentation rate are elevated). Diagnosis therefore necessitates careful clinical observation, in many cases during the second or third attack. Except for a positive tourniquet test (a test to assess the capillaries’ability to withstand increased pressure), coagulation and platelet function tests are usually normal. Small-bowel X-rays may reveal areas of transient edema; in many cases, tests for blood in the urine and stool are positive. Increased blood urea nitrogen and creatinine levels may indicate renal involvement. Diagnosis must rule out other forms of nonthrombocytopenic purpura.
Treatment
Treatment is generally symptomatic; for example, severe allergic purpura may require steroids to relieve edema and analgesics to relieve joint and abdominal pain. Some patients with chronic renal disease may benefit from immunosuppressive therapy with azathioprine along with identification of the provocative allergen. An accurate allergy history is essential.
Special considerations
❑ Encourage maintenance of an elimination diet to help identify specific allergenic foods so these foods can be eliminated from the patient’s diet.
❑ Monitor skin lesions and level of pain. Provide analgesics as needed.
❑ Watch carefully for complications: GI and GU tract bleeding, edema, nausea, vomiting, headache, hypertension (with nephritis), abdominal rigidity and tenderness, and absence of stool (with intussusception).
❑ To prevent muscle atrophy in the bedridden patient, provide passive or active range-of-motion exercises.
❑ Provide emotional support and reassurance, especially if the patient is temporarily disfigured by florid skin lesions.
❑ After the acute stage, stress the need for the patient to immediately report any recurrence of symptoms (recurrence is most common about 6 weeks after initial onset) and to return for follow-up urinalysis as scheduled.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
Other Book Chapters Related to Ecchymosis
Read excerpts from these other book chapters related to Ecchymosis:
Medical Books Excerpts
- Purpura
- "In a Page: Signs and Symptoms" (2004)
- [ read ]
- Purpura
- "In A Page: Pediatric Signs and Symptoms" (2007)
- [ read ]
- Petechiae
- "In A Page: Pediatric Signs and Symptoms" (2007)
- [ read ]
- Purpura
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
- [ read ]
- Purpura
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
- [ read ]
- Purpura
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
- [ read ]
- Purpura
- "Nursing: Interpreting Signs and Symptoms" (2007)
- [ read ]
Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Ecchymosis
» Next page: Idiopathic thrombocytopenic purpura (Professional Guide to Diseases (Eighth Edition))
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