Allergic purpura

Introduction to allergic purpura Allergic purpura, also known as hemorrhagic capillary venom, is a relatively common microvascular allergic hemorrhagic disease. The disease is a systemic vascular disease caused by allergic reactions of small arteries and capillaries to certain substances. The basic lesions are extensive aseptic inflammation of capillaries and arterioles, resulting in increased permeability of the vessel wall and exudative hemorrhage and edema. Clinically, skin purpura is the most common, and can be associated with symptoms of organs such as the gastrointestinal tract, joints, and kidneys. Therefore, allergic purpura is clinically divided into simple skin type, joint type, abdominal type, allergic purpura combined with nephritis type and mixed type. . basic knowledge Sickness ratio: 0.0012% Susceptible people: good for children and adolescents Mode of infection: non-infectious Complications: nephritis nephrotic syndrome hepatomegaly gastrointestinal bleeding asthma

Cause of allergic purpura

Autoimmune (30%):

As the body's allergic reaction to allergic substances causes capillary permeability and fragility, resulting in subcutaneous tissue, mucosa and internal organs bleeding and edema, allergens can be caused by a variety of factors, but for each specific case The exact cause is often difficult, and it is generally believed that it may be related to a variety of predisposing factors, but direct pathogenic factors are often difficult to affirm.

Infection factor (40%):

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.

Other factors (20%):

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. Allergic allergens enter the body and combine with the proteins in the body to form antigens. After a certain incubation period (5-20 days), the antigen stimulates immune tissues and plasma cells to produce IgE. IgE is adsorbed to the mast cells of various organs of the body. Above (vascular circumference, stomach cavity, skin), when it encounters the same antigen stimulation, the antigen binds to IgE adsorbed on mast cells, activates the enzyme system in the cell, and causes mast cells to release a series of organisms. Active substances such as histamine, 5-TH, bradykinin, allergic slow-reacting substance (SRS-A) can also excite sympathetic nerves and release acetylcholine. SRS-A is derived from leukotriene C4 (LTC4) and its metabolites. LTE, LTD4 consists of LTC4 transformed into LTD4 under the action of -glutamyltranspeptidase, which is converted to LTE4 by dipeptidase. This series of biologically active substances mainly acts on smooth muscle and causes small arteries. Capillary expansion, increased permeability, tissue, organ bleeding, edema.

2, antigen-antibody complex reaction This is the main pathogenesis, allergen stimulates plasma cells to produce IgG (also produces IgM and IgA), the latter binds to the corresponding antigen to form an antigen-antibody complex, the small molecule part of which is soluble, The blood can be deposited on the vascular wall or the glomerular basement membrane. C3a, C5a, C5, C6, and C7 produced by the activation of the complement system can attract neutrophils, which phagocytose the antigen-antibody complex and release lysosomes. Enzymes cause vasculitis, involving the corresponding organs. In another part of the immune complex, the antibody is more than the antigen. The complex has a large molecular weight and is precipitated by non-soluble ones. It is cleared by the mononuclear macrophage system and generally does not produce pathological changes. .

Allergic purpura prevention

[Rehabilitation Guide]

(1) The main measures for preventing the disease from avoiding its poison gas are as follows:

1. Prevent infections such as bacteria, viruses, parasites, etc., and actively prevent upper respiratory tract infections.

2, diet has a festival.

3, adjust the mood to keep the mood relaxed and happy.

(2) Life conditioning:

1, often participate in physical exercise, enhance physical fitness, prevent colds.

2. Actively remove infected lesions to prevent upper respiratory tract infections.

3, try to find allergens; prevent food, drugs, thorns, insect bites and other sensitization.

4, the acute phase and bleeding, the patient's activities should be limited.

(3) Diet conditioning: The disease is mainly blood and blood, the diet should be light, the staple food is rice, pasta, cornmeal, eat more fruits and vegetables, avoid eating fat and throat, spicy products, to prevent gastrointestinal heat. For foods that have been allergic to the disease, such as fish, shrimp, seafood and other absolute taboos, qi deficiency should be qi and nourishing to stop bleeding, blood stasis can be used to promote blood circulation.

Allergic purpura complications Complications nephritis nephrotic syndrome liver gastrointestinal bleeding asthma

1. Nephritis: It 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. Different, some only transient hematuria, and some quickly progress to renal failure, mainly manifested as gross hematuria (30%), proteinuria (<1g / d accounted for 50% to 60%) edema, high blood pressure, even visible Nephrotic syndrome (15% to 39% of urinary protein >3.5g/d), 80% of renal biopsy changes, 90% to 95% return to normal within weeks to months, and rare to develop 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 appears hematuria without systemic symptoms More common in young adults, it helps identify, renal biopsy shows segmental or rare diffuse glomerular proliferation, with capillaries blocked by fibrin-like substances.

2, occasionally have asthma, vaginal discharge caused by edema of the vocal cords is a serious complication, but relatively rare, there are reports of complicated myocardial infarction, hepatomegaly, ischemic necrotic cholangitis and testicular bleeding.

3, gastrointestinal bleeding: related to intestinal mucosal damage.

Symptoms of allergic purpura Common symptoms Papular rash skin purpura hypothermia bloody stool abdominal pain diarrhea nausea azotemia irritability proteinuria

1, purple cicada: often symmetric distribution, appear in batches, vary in size, color shades vary.

2, gastrointestinal manifestations: paroxysmal abdominal cramps or persistent dull pain, but also vomiting, diarrhea, blood in the stool.

3, joint performance: mainly joint pain, often accompanied by swelling, effusion and fever.

4, kidney performance: more common in children, more than 1 week after the appearance of purpura, can be expressed as proteinuria, hematuria, with oliguria, edema, high blood pressure and so on.

Examination of allergic purpura

1, blood test: white blood cells normal or increased, neutral and eosinophils can be increased; unless severe bleeding, generally no anemia; platelet count is normal or even elevated, bleeding and clotting time is normal, clot retraction test is normal, some children's hair Positive vascular fragility test, normal or rapid erythrocyte sedimentation rate, elevated serum IgA, mild elevation of IgG, IgM, normal or elevated C3, C4; antinuclear antibody and RF negative; severe plasma viscosity increased.

2, bone marrow: normal bone marrow, eosinophils can be high.

3, urine test: may have protein, red blood cells, white blood cells and casts, severe cases of gross hematuria.

4, fecal routine examination: some patients can see parasite eggs and red blood cells, occult blood test can be positive.

5, capillary fragility test: positive.

6, pathological examination: diffuse small perivascular inflammation, neutrophils gathered around the blood vessels, immunofluorescence showed that IgA and C3 in the dermal wall of the vascular wall.

7. 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 identification of allergic purpura

Diagnostic criteria

1, blood routine examination: blood cells mildly moderate, eosinophils normal or increased, bleeding volume can be more anemia, clotting time, platelet count, blood clot shrinkage time are normal.

2, ESR: Most patients have increased erythrocyte sedimentation rate.

3, anti-O: can be increased.

4, serum immunoglobulin: serum LGA can be increased.

5, urine routine: kidney affected by the presence of protein, red blood cells or casts in the urine.

6, blood urea nitrogen and Keegan: increased renal insufficiency.

7, fecal occult blood: yang when the gastrointestinal bleeding.

8. Capillary fragility test: About half of the patients are positive.

9, renal tissue biopsy: can determine the nature of nephritis lesions, the treatment and prognosis judgment has a guiding significance.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.