Pneumocystis carinii

Introduction to Pneumocystis carinii Pneumocystosis is a protozoan disease caused by Pneumocystis carinii infection. The main clinical manifestations are dry cough, dyspnea and cyanosis. Its pathogen is characterized by interstitial pneumonia, so it is called pneumocystis cariniipneumonia (PCP). The disease is more common in patients with low or weak immune function, which can be regarded as an opportunistic infection. Since the high incidence and mortality of AIDS patients have been found in the 1980s, the study of pulmonary cysticercosis, especially PCP, has gradually deepened. basic knowledge The proportion of the disease: 0.002% -0.003% (more common in low constitution and HIV infection) Susceptible people: good for children Mode of infection: respiratory transmission Complications: cytomegalovirus infection Toxoplasmosis

Causes of Pneumocystis carinii

Infection (30%):

Pneumocystis carinii is a eukaryotic microorganism. There are two main forms, namely, cysts and trophozoites. The early stage of encapsulation is an intermediate shape between the two. The morphological features are not clear, and the cysts are round or oval. , diameter 4 ~ 6m, capsule wall thickness 100 ~ 160nm, silver staining is brownish black, toluidine blue dyed purple blue, mature, cystic cytoplasm is absorbed, contains 8 intracapsular bodies, diameter 1 ~1.5m, pleomorphic, thin film, mononuclear, after cyst rupture, the small body of the capsule is released, develops into a trophozoite, the trophozoite is not colored, and is propagated by the two-splitting method, often in the lungs of severely infected people. A large number of trophozoites, and less cysts, cysts are an important basis for diagnosis.

Because its trophozoite has a pseudopod structure similar to protozoa, it can not grow in fungal culture medium, and is sensitive to antiprotozoal drugs. It is generally considered to belong to protozoa, sporozoite, but its ultrastructure is similar to fungi, its 16s ribosomal RNA Molecular analysis of mitochondrial DNA revealed that its phylogenetics are closely related to yeast ascomycetes, and the mitochondrial DNA nucleotide sequence is homologous to fungi (60%) over homologous to protozoa (only 20%). Therefore, it is currently believed that it should be attributed to fungi. Although traditional antifungal drugs such as amphotericin and pyrrole are not effective against it, at present, new antifungal drugs have been confirmed in foreign countries to inhibit -glucan aggregation in the in vitro infection model. The synthesis of sugar is also active in its trophozoites. Therefore, the taxonomic status of Pneumocystis carinii is still controversial, but most authoritative literature, textbooks have classified it as a fungus.

Acquired immunodeficiency (40%):

More common in AIDS, leukemia, lymphoma and other malignant tumors, connective tissue diseases or organ transplantation, a large number of long-term application of adrenocortical hormone, cytotoxic drugs or radiation therapy, can cause the body's immune function inhibition, an important cause of PCP.

A healthy person is often a latent infection after infection, which can cause a dominant infection in the following cases.

Premature or malnourished infants (15%):

More than 10 to 24 weeks after birth;

Congenital immunodeficiency (10%):

Including humoral immunity, cellular immunity or both;

Pathogenesis

Pneumocystis is a parasite with low pathogenicity and slow growth and growth. It adheres to the surface of human alveolar type I epithelial cells. It is a potential infection with alveolar leachate as a nutrient. When the host immune function is reduced, it is in a latent state. The protozoa began to multiply, causing direct damage to epithelial cells, impeding gas exchange, increasing lung volume, and liver-like changes. Typical histological lesions were infiltration of alveolar interstitial cells, mainly infiltration of plasma cells in infants and young children, adults or adults. Lymphocyte infiltration, mainly macrophages and eosinophils, if there is no secondary bacterial infection, there is very little neutrophil infiltration, alveolar space epithelial cell hyperplasia, thickening, partial shedding, may have The formation of a transparent film, interstitial fibrosis and edema, etc., the alveolar cavity is enlarged, and is filled with a foam-like honeycomb-like eucalyptus red substance, which contains a worm body, a disintegration substance thereof, and exfoliated epithelial cells.

Pathophysiological changes include hypoxemia, increased alveolar-arterial pressure difference (PaO2), respiratory alkalosis; diffuse force impairment, suggesting alveolar-capillary block; lung compliance changes, decreased lung capacity, The above changes may be related to the abnormality of the pulmonary surfactant system. Broncho-alveolar lavage fluid (BALF) analysis showed that the surfactant phospholipid component decreased and the protein increased. In vitro test showed that the protozoan inhibited the surfactant phospholipid group. The secretion of points.

Pneumocystis carinii prevention

Patients should be isolated from the respiratory tract, improve the nutritional status of patients, reduce unnecessary immunosuppressive chemotherapy, radiotherapy, and take preventive measures against susceptible populations, high-risk groups, such as compound sulfamethoxazole, TMP 5mg/kg per day, SMZ According to 25mg/kg per day, it is divided into two times orally, three times a week for 5 to 18 months. It can also be prevented by spray of chlorpyrifos, phenyl sulfone, etc. There is no vaccine available.

Complications of Pneumocystis carinii Complications, cytomegalovirus infection, toxoplasmosis

Complications include cytomegalovirus infection, tuberculosis, fungal infection or toxoplasmosis.

Symptoms of Pneumocystis carinii common symptoms dyspnea pleural effusion immunodeficiency dry cough nodule nasal wing fan vocal vocal sounds lungs comprehensed atelectasis

There are clinical manifestations of infection, roughly divided into two types.

Popular type

Also known as infant-type, more common in low-weight children, malnourished or congenital immunodeficiency in infants, concealed onset, respiratory increase is the earliest respiratory symptoms, later dry cough, difficulty breathing, nose flapping, cyanosis, etc. The morbidity rate of those who did not receive timely treatment reached 50%.

2. loose hair

Also known as children-adult type, more common in immunocompromised or defective, rapid onset, fever, cough, difficulty breathing, cyanosis, etc., but few voices, short course of illness can die within 4 to 8 days, X Line chest changes often later than clinical manifestations, such as no specific treatment, regardless of adult or child, the mortality rate is as high as 90% to 100%, the X-ray findings of both types of lungs are diffuse, bilateral or spotted shadows Pneumonia and lung base are less affected, and can rapidly develop lung consolidation. There are often extensive or limited emphysema in the consolidation lesions. In some cases, pneumothorax, pleural effusion, lung nodule shadow, etc. The arterial oxygen partial pressure is often lower than 10.7 kPa (80 mmHg), the C02 partial pressure is normal or low, and the arterial blood pH is often increased.

In addition to the above clinical manifestations, blood and pathogens were examined.

Examination of Pneumocystis carinii

Blood picture

The white blood cell count is normal or elevated, mostly (15 ~ 20) × 109 / L, the classification is normal or the left side of the nucleus, eosinophils can be slightly increased.

2. Pathogen examination

The sputum examination is the most convenient and safe. It can be precipitated by centrifugation, stained microscopy after smear, bronchoalveolar lavage or lung biopsy specimens, and the trophozoites and cysts of Pneumocystis carinii can be diagnosed. Applications such as toluidine blue staining and PCR technology have greatly improved the detection rate.

Diagnosis and identification of Pneumocystis carinii

The disease must be differentiated from viral pneumonia, chlamydia pneumonia, and tuberculosis.

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