Allergic purpura
Allergic purpura, or anaphylactoid purpura, is a type of nonthrombocytopenic purpura. It’s characterized by allergy symptoms and acute or chronic vascular inflammation affecting the skin, joints, or GI or genitourinary (GU) tract. 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). 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 for adults.
Causes
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, an 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, allergic reactions to insect bites, and allergic reactions to some foods (such as wheat, eggs, milk, and chocolate).
Signs and symptoms
Allergic purpura is characterized by purple skin lesions that are macular, ecchymotic, and varying in size, usually appearing in symmetrical patterns on the arms and legs. The lesions are caused by vascular leakage into the skin and mucous membranes and are accompanied by pruritus, paresthesia and, occasionally, angioneurotic edema. In children, the lesions are generally urticarial, and they usually 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 pain and periarticular effusion, 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.
Other signs and symptoms include moderate and irregular fever, headache, anorexia, and localized edema of the hands, feet, or scalp.
Diagnosis
No laboratory test result clearly identifies allergic purpura (although the white blood cell count and erythrocyte sedimentation rate are elevated). Diagnosis therefore requires careful observation, usually during the second or third attack. Except for a positive tourniquet test result, coagulation and platelet function test results are usually negative. X-rays of the small bowel may reveal areas of transient edema; test results for blood in the urine and stool are often positive. Increased blood urea nitrogen and serum creatinine levels may indicate renal involvement. The diagnosis must rule out other forms of nonthrombocytopenic purpura.
Treatment
Most patients with Henoch-Schönlein syndrome recover completely. When therapy is required, the glucocorticoid prednisone is given in doses of 1 mg/kg, and tapered to response, to relieve edema. An analgesic may be given to relieve joint and abdominal pain. Some patients with chronic renal disease may benefit from intensive plasma exchange combined with an immunosuppressant, along with identification of the provocative allergen. An accurate allergy history is essential.
Special considerations
Encourage the patient to maintain an elimination diet to help identify specific allergenic foods so that these foods can be eliminated from his diet.
Monitor skin lesions and level of pain. Provide an analgesic, if needed.
CLINICAL TIP: 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 a bedridden patient, provide passive or active range-of-motion exercises.
After the acute stage, stress the need for the patient to immediately tell the physician of any recurrence of symptoms (recurrence is most common about 6 weeks after the initial onset) and to return for follow-up urinalysis as scheduled.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright Details: Handbook of Diseases, Copyright © 2008 Williams & Wilkins.
More About Causes of Bleeding under skin
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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