Pediatric visceral larva migrans

Introduction to visceral larval migration in children Visceral larvae transition syndrome, Löffler syndrome, also known as simple eosinophilic pulmonary infiltration (PIE), PIE syndrome, eosinophilic hepatomegaly (pediatric), eosinophils Pneumonia, migratory pneumonia, allergic pneumonia, etc., is a kind of allergic syndrome in the lungs, refers to the disease of pulmonary eosinophil infiltration and peripheral blood eosinophilia without obvious cause. Its clinical features are short-term and easily disappearing infiltrates in the lungs of patients, accompanied by eosinophilia and X-rays showing patchy shadows. basic knowledge The proportion of sickness: 0.0001% - 0.0003% Susceptible people: children Mode of infection: digestive tract spread Complications: respiratory failure pulmonary fibrosis

Etiology of pediatric visceral larvae

Parasitic infections (30%):

The most common infection is sputum infection. After eating the mites, the larvae hatch in the small intestine, then enter the liver along the portal vein through small blood vessels, and the blood flows to the lungs, causing lung infiltrates. Others are hookworms, whipworms, and schistosomiasis. , paragonimiasis, Clonorchis sinensis, filarial infections.

Recent studies have found that Toxocara canis infection is one of the causes of this disease. Canine mites are common parasites in dogs, and their larvae can also infect humans and develop visceral larval migration syndrome. The number of children infected with C. elegans infection is also increasing. The detection of canine nematode antibody in serum by Hailian immunosorbent assay (ELISA) is helpful for pathogenic diagnosis. Some people have 20 cases of visceral larvae transition syndrome. 10 patients with positive serum antibody test accounted for 50%.

Drug or food allergy (30%):

Most of the drugs are sulfa drugs, aspirin, penicillin and anti-venom. In foods such as milk, eggs, shrimps, crabs, fish, etc., the symptoms can be resolved after stopping or stopping eating allergic foods. In children with allergic constitution of allergic diseases, such as bronchial asthma, urticaria, etc., when a respiratory infection occurs, it can cause lung disease.

Inhaled allergic substances (30%):

Such as impatiens, hay pollen or spores of aspergillus. The reason is not easy to detect some cases, clinical respiratory symptoms and blood eosinophils, and the reasons are not easy to detect.

Pathogenesis

When the sensitizer inhales an organic dust or animal protein particles again, it causes an inflammatory reaction in the terminal segment of the lung. Type III hypersensitivity is the main pathogenesis of the disease, and specific IgG antibodies are present in more than 50% of the exposed persons. And in more than 90% of patients with clinical manifestations, the symptoms begin 4 to 8 hours after antigen challenge, and an antigen-antibody complex is formed and deposited in the interstitium of the lung, and then the complex activates complement to cause acute inflammation and tissue damage. Later, it was confirmed that cell-mediated type IV hypersensitivity also plays an important role in the pathogenesis of this disease. Type I hypersensitivity reaction does not play a significant role in the pathogenesis of typical allergic pneumonia, generally peripheral blood eosinophils The level of serum IgE is normal, the rate of rapid response to common inhaled allergen skin test is not high, and the incidence of atopic disease is also low. These two points indicate that atopy is unlikely to be an important risk factor for host susceptibility. Associated with the individual's genetic constitution and pre-existing lung disease.

The main pathological features are a large number of eosinophil infiltration in the alveolar cavity, pulmonary fibrosis and giant cell granuloma formation.

Pediatric visceral larvae migration prevention

The primary problem for the prevention and treatment of allergic patients is to find out the cause of allergies and prevent them. This is of preventive significance for non-existing patients, and it has therapeutic significance for patients with episodes. It can be summarized as a way to avoid allergic causes. For four words, namely: "avoid", "taboo", "replace", "shift".

Prevention of visceral larval migration syndrome should emphasize hygiene and develop good hygiene habits, such as washing hands before meals, preventing parasitic infections, and regularly deworming in early childhood, and using specific desensitization if necessary.

Complications of visceral larval migration in children Complications, respiratory failure, pulmonary fibrosis

Anti-recurrent authors cause irreversible tissue damage to the lungs and can progress to pulmonary fibrosis to chronic respiratory failure and heart failure.

Pediatric visceral larva migration symptoms common symptoms tired appetite loss, dry cough, anorexia, chills, high fever, asthma, pulmonary fibrosis, liver enlargement

Mild or no heat, only slightly hot, conscious fatigue, loss of appetite, weight loss, night sweating, mild dry cough; severe cases may have high fever, paroxysmal paroxysmal cough, may be associated with adhesion, even hemoptysis, difficulty breathing The auscultation of the lungs has wheezing or wet voices; the percussion sometimes has voiced sounds, and the younger children often have hepatomegaly. The course of the disease is limited to one month. The clinical condition is acute and chronic, to the intensity of exposure to the antigen and Frequency depends.

Acute allergic pneumonia

Often occurring after a short and strong antigen exposure, its performance is similar to acute bacterial and viral pneumonia. The sensitized person suddenly starts to cough, fever, chills, general malaise, and obvious dyspnea after 4-8 hours of exposure to the antigen. Physical examination can be seen in acute illness, rapid breathing, severe cyanosis, wet sputum in the lungs, and frequent increase of white blood cells. Generally, it will heal several days to several weeks after the antigen exposure stops. If the patient is hospitalized, it will quickly improve. The improvement is often mistaken for the effect of antibiotics. In fact, the most likely result is the natural result of avoiding the antigen. Because the diagnosis is unknown, the patient will return to the original place after discharge, and the symptoms will re-emerge. Such repeated exposure will eventually lead to irreversible patients. Lung tissue damage, X-ray examination of the chest in the acute phase showed minimal nodular infiltration of interstitial and alveolar, mostly patchy or diffuse distribution, nodules ranging in diameter from one to several millimeters, acinar type Shadow, hilar lymph nodes generally do not increase, the degree of abnormal chest X-ray examination reflects the severity of the disease, occasionally, in acute attacks, especially in the violence After the early detection of lung can be completely normal.

2. chronic allergic pneumonia

Due to exposure to a less concentrated antigenic environment or repeated episodes over a longer period of time, 50% of cases are insidious progression until pulmonary fibrosis, typically characterized by progressively worsening dry cough, difficulty breathing, anorexia and fatigue, etc. It is noticed when the lungs have been extensively fibrotic with pulmonary insufficiency. At this time, there may be manifestations of chronic respiratory failure and congestive right heart failure, which is difficult to distinguish from primary pulmonary fibrosis. Chest X-ray examination shows Extensive interstitial fibrosis with thickening of the image (texture) of the bronchial vessels.

Pediatric visceral larval migration

1. Peripheral blood test

Eosinophils in the surrounding blood are larger than normal, and contain large particles, the number of cells increases, accounting for 20% to 70% of the total number of white blood cells, and the direct count of eosinophils is usually around 3.0×109/L.

2. Immunological examination

The parasite antibody test in the blood can be positive; the IgE can be as high as 2300 ng/ml, and those with hepatomegaly often show hyperglobulinemia.

3. Parasitic egg inspection

Alveolar lavage fluid and 24h parasite eggs can be found positive.

4. Skin test

The skin test of the parasite skin test can be positive.

5. Chest X-ray film

It shows cloud-like patchy patches, which can be large or small. Shadows can disappear in a short period of time, and soon appear again. The parts can migrate without being constant, and sometimes can show atelectasis.

6. Pulmonary function test: The disease is mainly restrictive pulmonary dysfunction, the lung volume is significantly reduced in the acute phase, but there is no change in the spirometry, FVC is reduced, FEV1 is slightly decreased, and interstitial inflammation makes lung compliance (lung compliance) Reduced, obvious ventilatory blood flow abnormalities lead to decreased lung capacity and arterial oxygen partial pressure. As with clinical and X-ray changes, acute pulmonary dysfunction is reversible, to the chronic stage of extensive pulmonary fibrosis, restrictive And obstructive pulmonary dysfunction becomes irreversible.

Diagnosis and diagnosis of visceral larvae in children

diagnosis

According to clinical manifestations of respiratory symptoms including cough, asthma, fever, etc., as well as temporary infiltrative shadows in X-ray films, and increased eosinophils in the surrounding blood, diagnosis can be made.

In the medical history, the history of medication, food history and other allergic history should be asked in detail. The absolute value of eosinophils in the surrounding blood exceeds 3.0×109/L, which supports the diagnosis of this disease. The blood IgE measurement is high, if it is suspected to be due to dogs, Cat mites migrated in the body to cause this disease. They can be used in enzyme-linked immunosorbent assay (ELISA) to detect antibodies against dogs and cat mites, which are differentiated from infected mites. The eggs in the stool are found in lung lesions. It can be seen from a few days to a few weeks, so it is necessary to repeat the stool examination several times in the early stage of the disease and within 2 to 4 weeks after the disease to confirm the pathogen.

Differential diagnosis

Acute allergic pneumonia needs to be differentiated from some pulmonary interstitial diseases such as viral pneumonia, interstitial pulmonary edema, toxic drug reaction, sarcosis and acute primary interstitial pneumonia. Pneumonia, the difference between allergic bronchopulmonary aspergillosis.

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