What Is Allergic Purpura?

Allergic purpura (anaphylactoid purpura), also known as Henoch-Schonlein purpura (Henoch-Schonlein purpura), also known as self-limiting acute bleeding, is an allergic vasculitis that invades the skin and other organs' small arteries and capillaries. It may be that pathogen infection, certain drug effects, allergies, etc. cause the body to form IgA or IgG circulating immune complexes, which are deposited in the capillaries of the upper dermis and cause vasculitis. The main manifestations are purpura, abdominal pain, joint pain, and kidney damage, but the platelets do not decrease. Some people think that allergic purpura and allergic skin vasculitis belong to the same spectrum of diseases. This disease is the most common type of vasculitis in childhood. It occurs mostly in school-age children. The common age of onset is 7 to 14 years, and infants less than 1 year old are rare.

Basic Information

nickname

Henoch-Schonlein purpura, self-limiting acute hemorrhage

English name

Schoenlein-Henoch purpura

Visiting department

Division of Rheumatology

Multiple groups

Children 7 to 14 years

Common locations

Extremities extended, especially both lower limbs and hips

Common causes

May be related to streptococcal infections, viral infections, drugs, etc.

Common symptoms

Skin purpura with abdominal pain, joint pain, hematuria, proteinuria, etc.

Contagious

no

Causes of allergic purpura

The cause and mechanism have not been fully elucidated so far, and may be related to streptococcal infection, viral infection, drugs, food, insect bites, etc. The mechanism is due to the combination of antigens and antibodies to form immune complexes that deposit on the vessel wall, activate complement, and cause capillaries Inflammation of the small blood vessel wall and its surroundings increases the permeability of the blood vessel wall, which results in various clinical manifestations.

Clinical manifestations of allergic purpura

Occurs in children and adolescents, with fever, headache, joint pain, and general discomfort.

Skin

Skin purpura is the first symptom. Skin lesions can range from needles to soybean-sized petechiae, petechiae, or urticaria-like rashes or pink maculopapular rashes. Purpura can fuse into tablets and eventually turn brown. Usually subsides within 1 to 2 weeks without leaving any traces. In severe cases, blisters, blood blister, necrosis and even ulcers can occur. The rash mostly occurs in weight-bearing areas, and it usually occurs in the extremities of the extremities, especially the lower extremities, around the ankles and hips. The lesions are symmetrically distributed, appear in batches, and easily recur. People with only skin damage are also called simple purpura,

2. Digestive system

Gastrointestinal symptoms develop in about two thirds of cases. It usually appears within one week after the rash occurs. Common abdominal pain, mostly manifested as paroxysmal umbilical pain, colic, abdominal pain can also occur in other parts of the abdomen. There may be tenderness and rare rebound pain. Accompanied by vomiting. About half of the children are positive for occult blood in the stool, some may have bloody stool, and even vomit. If abdominal pain occurs before skin symptoms, it is easy to be misdiagnosed as surgical acute abdomen, or even surgical treatment. A small number of children may be complicated by intussusception, intestinal obstruction, intestinal perforation, and hemorrhagic enteritis. Patients with abdominal pain, diarrhea, blood in the stool, and even gastrointestinal bleeding are also called gastrointestinal purpura.

3. Urinary system

Most patients develop gross hematuria or microscopic hematuria and proteinuria, or cast urine 2 to 4 weeks after purpura. Urinary symptoms can occur at any time during the course of the disease, or after the rash subsides or the disease is at rest. The severity of the disease ranges from severe renal failure to hypertension. Kidney damage in more than half of children can be cured on their own. With hematuria, proteinuria, renal damage are also called renal purpura.

4. joint

Most children show swelling, pain, tenderness, or arthritis in and around the joints, which can be accompanied by restricted movement. Large joints such as knee and ankle joints are most commonly affected, and wrist, elbow, and fingers are also affected. Joint lesions are often transient and disappear within a few days without leaving joint deformities. People with joint swelling, pain, or even joint effusion are called joint purpura.

5. Other

Central nervous system symptoms are rare and manifest as coma, subarachnoid hemorrhage, optic neuritis, and Guillain-Barre syndrome.

Allergic purpura test

Hematological examination

Platelet count is normal or elevated. Bleeding time, clotting time, and clot contraction time were all normal. In some children, the total number of white blood cells increased up to 20.0 × 10 ⁹ / L, with the nucleus shifting to the left. ESR can increase faster.

2. Infection and etiological examination

Increased C-reactive protein and anti-streptococcus hemolysin can be positive, hemolytic streptococcus can be seen in pharyngeal culture.

3. Immunological examination

Antinuclear antibodies and rheumatoid factors are often negative. About half of the children's serum IgA, IgM increased during the acute phase.

4. Occult blood test

In children with gastrointestinal symptoms such as abdominal pain, fecal occult blood may be positive.

5. Urine routine

Microscopic hematuria and gross hematuria can occur when the kidney is affected. Sometimes severe proteinuria can cause hypoproteinemia.

6. Imaging examination

For those with gastrointestinal symptoms, abdominal B-mode ultrasound and X-ray examination can be performed, which is helpful for the early diagnosis of intussusception.

Allergic Purpura Diagnosis

It is not difficult to diagnose those with typical symptoms such as purpurs of the lower extremities, with abdominal pain, joint pain or kidney damage. However, when systemic symptoms such as joint pain and abdominal pain appear before skin purpura, it is easy to be misdiagnosed as rheumatoid arthritis or acute abdomen, and it needs to be clinically distinguished from these diseases and other types of purpura and vasculitis.

Differential diagnosis of allergic purpura

Idiopathic thrombocytopenic purpura

It is generally not difficult to distinguish the rash based on its morphology, distribution, and platelet count.

2. Surgical Acute Abdomen

If acute abdominal pain occurs before the rash appears, it should be distinguished from acute abdomen. Allergic purpura has more severe abdominal pain, but its position is not fixed and tenderness is mild. Unless bowel perforation occurs, there is generally no abdominal muscle tension and rebound pain. If bloody stool occurs, it needs to be identified with intussusception and Merkel diverticulum.

3. Bacterial infection

Meningococcal bacteremia, sepsis, and subacute bacterial endocarditis can all develop purpuric rash. The purpura of these diseases may have necrosis at the center. The general condition is critical, and positive blood culture can be identified.

4. Kidney disease

Renal symptoms should be distinguished from glomerulonephritis and IgA nephropathy after streptococcal infection.

5. Other

It also needs to be distinguished from systemic lupus erythematosus, diffuse intravascular coagulation and hemolysis, and uremia.

Allergic Purpura Treatment

Cause treatment

Actively look for and treat possible causes. The vast majority of allergic purpura is difficult to find obvious causes, and it is easy to recur, and it is difficult to completely cure. Pure skin purpura is mainly rest, and it is not appropriate to over-treat.

2. General treatment

The acute phase should rest in bed. Pay attention to the amount of fluid in and out, strengthen nutrition, and maintain electrolyte balance. Gastrointestinal bleeding is only manifested when fecal occult blood is positive, such as abdominal pain is not serious, liquid food can be used. Those with severe gastrointestinal bleeding should fast. Look for and avoid allergens. Symptomatic treatment, fever, joint pain can use antipyretics and analgesics such as indomethacin, fenpyridine; abdominal pain should be used antispasmodics, such as anisodamine orally or intramuscularly, or atropine intramuscularly Effective antibiotics.

3. Antihistamines

For simple purpura, rutin, vitamin C, calcium, Anluoxue or hemostatic can be used at the same time. When there is urticaria or angioedema, antihistamines and calcium are applied; in recent years, H2 receptor blocker cimetidine has been proposed for treatment.

4. Antiplatelet agglutination drugs

Aspirin is taken orally once a day; pansentin is taken in divided doses.

5. Anticoagulation therapy

The disease can be manifested by fibrinogen deposition, platelet deposition, and intravascular coagulation. Therefore, heparin has been used in recent years, or urokinase has been used.

6. Adrenal corticosteroids

Suitable for severe skin damage or joint, abdominal, and renal purpura. Indications for hormone use:

(1) Severe gastrointestinal diseases, such as prednisone, or dexamethasone and methylprednisolone when the gastrointestinal bleeding occurs, can be stopped after the symptoms are relieved

(2) Prednisone can be used in patients with nephrotic syndrome, not less than 8 weeks;

(3) Radical nephritis can be treated with methylprednisolone in the same dose as lupus nephritis. If hormone therapy fails, immunosuppressants such as cyclophosphamide can be added.

7. Plasma exchange

This method can effectively remove immune complexes in the blood circulation, thereby preventing vascular occlusion and infarction. It is suitable for severe abdominal and renal patients with a large number of immune complexes in plasma.

8. Other

For severe cases, high-dose gamma globulin shock treatment can be used.