Allergic purpura in children

Introduction to allergic purpura in children Allergic purpura (allergicpurpura), also known as hemorrhagic capillary venom or Henoch-Schönlein syndrome, is a more common type of capillary allergic disease, mainly involving the skin, mucous membranes, gastrointestinal, joint and kidney. The capillary wall of the site increases its permeability and fragility, causing bleeding symptoms. basic knowledge The proportion of sickness: 0.00352% Susceptible people: children Mode of infection: non-infectious Complications: nephritis, hematuria, nephrotic syndrome

Pediatric allergic purpura

(1) Causes of the disease

May be related to a variety of predisposing factors, but direct pathogenic factors are often difficult to affirm.

Infection factor

The most common bacterial infection is -hemolytic streptococcus, followed by Staphylococcus aureus, Mycobacterium tuberculosis, Salmonella typhi, Pneumococcal and Pseudomonas, etc. The above respiratory tract inflammation is more common, also seen in pneumonia, tonsillitis, scarlet fever , bacillary dysentery, urinary tract infection, impetigo, tuberculosis and focal infections (skin, teeth, mouth, middle ear), etc., viral infections include rubella, flu, measles, chickenpox, mumps, hepatitis, etc., parasitic infections Can cause this disease, more common with aphid infection, as well as hookworm, whipworm, aphid, schistosomiasis, vaginal trichomoniasis, malaria parasite infection.

2. Food factors

Mainly due to animal allergy protein caused by allergies to the body, fish, shrimp, crab, cockroach, eggs, chicken and milk can cause this disease.

3. Drug factors

Drugs such as chloramphenicol, streptomycin, isoniazid, aminopyrine, aspirin, sulfonamides, etc. have all reported this disease.

4. Other factors

Insect bites, plant pollen, cold, trauma, menopause, tuberculin test, vaccination, mental factors, etc. can also be caused by hemodialysis patients, lymphoma chemotherapy patients and Guillain-Barre syndrome patients Report of allergic purpura.

(two) pathogenesis

Under the sensitization of the above factors, allergic reactions occur in the body, and the mechanism is as follows:

1. Immediate allergic reaction

After the allergen enters the body, it combines with the protein in the body to form an antigen. After a certain incubation period (5-20 days), the antigen stimulates the immune tissue and plasma cells to produce IgE. IgE is adsorbed on the mast cells of various organs of the body (perivascular, stomach). Cavity, skin), when it encounters the same antigen stimulation, the antigen binds to IgE adsorbed on the mast cells, activates the enzyme system in the cell, and causes the mast cells to release a series of biologically active substances, such as histamine. , 5-TH, bradykinin, allergic slow-reacting substance (SRS-A), can also excite sympathetic nerves, release acetylcholine, SRS-A is composed of leukotriene C4 (LTC4) and its metabolites LTE, LTD4, LTC4 is converted to LTD4 by -glutamyltranspeptidase, which is converted to LTE4 by dipeptidase. This series of biologically active substances mainly acts on smooth muscle, causing small arteries, telangiectasia, and transparency. Increased sex, tissue, organ bleeding, edema.

2. Antigen-antibody complex reaction

This is the main pathogenesis, and allergens stimulate plasma cells to produce IgG (also producing IgM and IgA), which binds to the corresponding antigen to form an antigen-antibody complex. The small molecule is soluble and can precipitate in the blood vessel wall or On the glomerular basement membrane, C3a, C5a, C5, C6, and C7 produced by the activation of the complement system can attract neutrophils, which phagocytose antigen-antibody complexes, release lysosomal enzymes, cause vasculitis, and involve In organs, in another part of the immune complex, the antibody is more than the antigen, and the complex has a large molecular weight and is precipitated by the non-soluble one, and is cleared by the mononuclear macrophage system, and generally does not cause pathological changes.

3. The role of cytokines

It has been reported that the serum levels of TNF and soluble TNF receptor (sTNFR) in patients with allergic purpura are in the normal range, while the level of sIL-2R is elevated. In renal local tissue cells of patients with allergic purpura with renal injury, there are many The expression of inflammatory factors such as IL-1, IL-1, TNF- and LT has recently been reported to increase the level of IL-4 in patients with allergic purpura, especially in the acute phase, which is the upper limit of normal people. More than 40 times, suggesting that cytokines are involved in the pathogenesis of allergic purpura, IL-4 promotes IgE synthesis, which may be an important factor in the course of the disease.

Pediatric allergic purpura prevention

1. Prevent infections such as bacteria, viruses, parasites, etc.

2. Prevent food, drugs, thorns, insect bites and other sensitization.

3. Actively prevent upper respiratory tract infections.

Pediatric allergic purpura complications Complications nephritis hematuria nephrotic syndrome

1. Nephritis is one of the most common complications of this disease. Its incidence rate is 22% to 60% in foreign countries, and 12% to 49% in domestic reports. It usually occurs within 1 to 8 weeks after the appearance of purpura. First, some only have transient hematuria, and some quickly progress to renal failure, mainly manifested as gross hematuria (30%), proteinuria (<1g/d accounted for 50% to 60%) edema, hypertension, occasionally visible nephropathy Syndrome (15% to 39% of urinary protein > 3.5g / d), 80% of patients with a certain degree of renal biopsy, 90% to 95% returned to normal within weeks to months, rare to develop into chronic ( 6%), a small number can be expressed as nephrotic syndrome, nephritis caused by allergic purpura and IgA nephritis sometimes can not be distinguished, but mononuclear and T cell infiltration is only seen in the former, and IgA nephritis often shows hematuria without systemic symptoms. More common in young adults, to help identify, renal biopsy showed segmental or rare diffuse glomerular proliferation, with capillaries blocked by fibrin-like substances.

2. Occasionally, asthma, edema of the vocal cords is a serious complication, but it is rare, there are reports of complicated myocardial infarction, hepatomegaly, ischemic necrotic cholangitis and testicular bleeding.

Symptoms of allergic purpura in children Common symptoms Thrombocytopenia skin purpura pimples purpura nose bleeding bleeding gums abdominal pain joint swelling and constipation black stool

Mostly acute onset, the first symptom is mainly skin purpura, some cases of abdominal pain, arthritis or kidney symptoms first appeared, 1 to 3 weeks before onset, often have a history of upper respiratory tract infection, may be associated with low fever, anorexia, fatigue, etc. Systemic symptoms.

1. The skin purpura repeatedly appears in the course of skin purpura. It is common in the limbs and buttocks. It is symmetrically distributed and has more stretching sides. It appears in batches with less facial and trunk. It is purple-red rash and high in the beginning. The face, followed by a brownish color, can be accompanied by urticaria and angioedema. In severe cases, the purpura can be fused into a bullous with hemorrhagic necrosis.

2. More than half of children with digestive tract symptoms have repeated paroxysmal abdominal pain, located in the umbilical or lower abdomen, with severe pain, may be associated with vomiting, but vomiting is rare; some children have melena or bloody stools, diarrhea or constipation, occasionally Concurrent intussusception, intestinal obstruction or intestinal perforation.

3. Joint symptoms appear knee, ankle, elbow, wrist and other large joint swelling and pain, limited activity, single or multiple, fluid in the joint cavity, can disappear within a few months, leaving no sequelae.

4. Renal symptoms The kidney disease caused by this disease is the most common secondary glomerular disease in children. The kidney symptoms are different. Most of the children have hematuria, proteinuria and cast, with increased blood pressure and edema. Purpuric nephritis, a small number of nephrotic syndrome manifestations; the majority of renal symptoms appear within 1 month of onset, can also occur in the later stages of the disease, a few with nephritis as the first symptom; although some children with hematuria, proteinuria continued Months or even years, but most can be fully restored, a small number of developments to chronic nephritis, died of chronic renal failure.

5. Other occasional intracranial hemorrhage, leading to convulsions, paralysis, coma, aphasia, but also nose bleeding, bleeding gums, hemoptysis, testicular bleeding and other bleeding, occasionally involving the circulatory system of myocarditis, pericarditis, or involving the respiratory system Laryngeal edema, asthma and pulmonary hemorrhage.

Examination of allergic purpura in children

1. Blood leukocytes are normal or increased, neutral and eosinophils can be increased; unless severe bleeding, generally no anemia; normal or even elevated platelet count, normal bleeding and clotting time, normal clot retraction test, capillary fragility in some children The test was positive.

2. Urine routine can have red blood cells, protein, cast, severe cases of gross hematuria.

3. Fecal occult blood test for patients with gastrointestinal symptoms, fecal occult blood test more positive.

4. Blood test for normal or rapid erythrocyte sedimentation rate, serum IgA can be elevated, IgG, IgM can be mildly elevated; C3, C4 is normal or elevated; antinuclear antibody and RF are negative; severe plasma viscosity is increased.

5. Abdominal ultrasound examination is helpful for early diagnosis of intussusception; head MRI can be diagnosed in children with central nervous system symptoms; kidney symptoms are heavier and prolonged children can be treated with renal puncture to understand the condition and give corresponding treatment.

Diagnosis and diagnosis of allergic purpura in children

Diagnostic criteria

Typical case diagnosis is not difficult. If the clinical manifestations are not typical, skin purpura does not appear, it is easy to be misdiagnosed as other diseases, and needs to be differentiated from primary thrombocytopenic purpura, rheumatoid arthritis, surgical acute abdomen.

Typical skin symptoms, such as purpura in the thigh extension and hips appear in batches, symmetric distribution, size, diagnosis is not difficult, acute abdominal pain, joint pain and urine changes are also helpful for diagnosis, 1990 American rheumatism The new diagnostic criteria for allergic purpura that the society has developed are as follows:

1. Tactile purpura.

2. The age of onset is <20 years old.

3. Acute abdominal pain.

4. Tissue sections showed neutrophil infiltration around the venules and arterioles.

Among the above four criteria, two or more patients can be diagnosed as allergic purpura. The sensitivity of this standard is 87.1% and the specificity is 87.7%.

Differential diagnosis

1. The skin type needs to be differentiated from drug eruption or thrombocytopenic purpura. The drug rash has a certain history of medication. The rash is often distributed throughout the body. After stopping the drug, the drug rash can disappear. The plaque of thrombocytopenic purpura can be irregularly distributed. No uplift, no papules, urticaria, etc., decreased platelet count, prolonged bleeding time, no change in bone marrow.

2. Articular joint swelling and pain should be differentiated from rheumatoid arthritis, the latter often have rheumatic activity, serum anti-"O" antibody and erythrocyte sedimentation rate increased and increased significantly, mainly for acute migration, asymmetry multiple joints Inflammation, redness, swelling, heat and tenderness, limited movement, etc., can help identify.

3. Abdominal abdominal pain type allergic purpura patients should be differentiated from acute abdomen, the former in addition to abdominal pain, diarrhea, generally no muscle tension and rebound tenderness, and acute abdomen in addition to abdominal pain, there are muscle tension and rebound Pain, etc., can help identify.

4. Kidney type needs to be differentiated from acute glomerulonephritis, lupus nephritis, kidney tuberculosis, glomerulonephritis without skin purpura, abdominal and joint symptoms, lupus nephritis with multiple organ damage, leukopenia, erythrocyte sedimentation rate, Lupus cells are positive and other immune indicators are positive.

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