Capsular histoplasmosis

Introduction to capsular histoplasmosis Histoplasmosis capsular is a granulomatous disease that is widespread throughout the world caused by capsular histoplasmic capsular variants. basic knowledge The proportion of illness: 0.005% - 0.006% Susceptible people: no special people Mode of infection: non-infectious Complications: hemoptysis pneumonia

The cause of capsular histoplasmosis

(1) Causes of the disease

Histoplasma is divided into three varieties: capsule variants, Dubo varieties and sausage variants. It has been found that the first two variants are of the dermatitis Ayellomus (synonym capsular immonia), and the fungi are classified. Into the ascomycete - the genus of the genus, the genus, is a biphasic fungus, and the three variants cause different histoplasma, named capsular histoplasmosis, and Dubo cytoplasmic disease. And sputum histoplasmosis.

The capsular histoplasmic capsular variant was detected by Darling in the canal area of Panama in the United States in 1905. This type is highly susceptible to infection and should be prevented. The capsular histoplasma Dubo variant is 1952 Dubois. A stable variant of the capsular histoplasma found in South Africa, the capsular histoplasma sausage variant was first proposed by Week et al in 1985.

The capsular histoplasmic capsular variant can be isolated in the soil and air of the epidemic areas. Animals such as horses, dogs, cats and rats can be infected. The average temperature is 22-29 °C, and the relative humidity is 67%. In 87% of the regions, mainly in the tropics, subtropical and temperate regions, the incidence is higher, while in some parts of Europe it is less common.

(two) pathogenesis

Pulmonary histoplasmosis: due to inhalation of dust, can cause acute infection, 95% of cases are asymptomatic, leaving only calcification, tissue cytoplasmin skin test and fungal culture positive, chest radiograph showing lung Department scattered infiltration, hilar lymph node enlargement, and finally left a uniform distribution of calcification, disseminated histoplasmosis: can be a benign course, such as lung, liver, spleen and other organs can have many calcifications, but no Symptoms, under certain conditions, such as decreased immunity, can be progressive, disseminated or fulminant, progressive or disseminated more common in adults, with severe symptoms and hepatosplenomegaly, most of the violent hair is seen in children , especially babies, can quickly lead to death.

Prevention of capsular histoplasmosis

The hyphae type of this strain is highly infectious, and laboratory work should be taken care of. People who are in the first epidemic area should pay special attention to prevent infection due to poor immunity. Bird cages, chicken nests and bat caves often have this bacteria. Pollution should be taken care of.

Complications of capsular histoplasmosis Complications hemoptysis pneumonia

Severe cases may have weight loss, weakness, night sweats and hemoptysis, which is similar to tuberculosis. About 10% of patients in epidemic areas suddenly have more serious symptoms such as high fever, shortness of breath, chest pain, and similar acute pneumonia due to inhalation of a large number of spores.

Symptoms of capsular histoplasmosis Common symptoms High heat dry cough, night sweat, hemoptysis, weak immunity, chest pain, granuloma, weight loss, lymphadenopathy

Pulmonary histoplasmosis

Inhalation of bacteria-borne dust can cause acute infections, 95% of cases are asymptomatic, leaving only calcification after treatment, a few may have mild or moderate symptoms, such as dry cough, chest pain, children may have fever, severe cases may have Weight loss, weakness, night sweats and hemoptysis, quite similar to tuberculosis, tissue cytoplasmin skin test and fungal culture positive, chest radiograph showing lung infiltration, hilar lymph node enlargement, and finally leaving evenly distributed calcification points, in endemic areas About 10% of patients have severe symptoms such as high fever, shortness of breath, chest pain, and similar acute pneumonia due to inhalation of a large number of spores. The histoplasmin test is strongly positive.

2. disseminated histoplasmosis

Can be a benign course, such as lung, liver, spleen and other organs can have many calcification points, but asymptomatic, under certain conditions, such as decreased immunity, can be progressive, disseminated or fulminant, progressive Or disseminated more common in adults, with severe symptoms and hepatosplenomegaly, fulminant hair is mostly seen in children, especially babies, can quickly lead to death, a few cases can be converted to chronic or manifested as skin mucosal ulcers or granulomas, appearing in The mouth, tongue, throat, gastrointestinal tract, external genitalia or skin, bones and joints are rarely affected, and primary skin infections are rare, even in laboratory workers.

Examination of capsular histoplasmosis

Early primary pulmonary infection is mainly based on the histoplasmin skin test, combined with X-ray examination, disseminated cases should be based on mycological examination and serum test.

1. Histoplasmin skin test

It was first applied by van Permis in 1941. It was standardized by Emmons several years later. It was made by incubating the mycelial phase filtrate on asparagine glucose medium at 25 ° C for 2 to 4 months. This is related to the culture of "OT". Similarity, no sensitization, generally 1:100 or 1:1000 dilution, when the local hardening of 5mm after intradermal injection for 48h, it is considered positive, can cross-react with dermatitis buds and coccidioides .

2. Mycological examination

(1) Direct microscopic examination: It is still difficult to find the bacteria directly from the sputum. The KOH smear is often negative. It can be taken from the leukocyte layer and biopsy after blood centrifugation. The sternum puncture material is used for smear. First fixed with methanol for 10min, and then stained with Giemsa, the bacteria are often located in macrophages, the diameter is about 2 ~ 4m, often oval, with buds at the smaller end, the buds are very fine, can fall off when dyed, There is a circle of unstained halo around the cell, which is a cell wall. There is a large vacuole in the cell. Although the cell is often located in macrophages or monocytes, it can also be located outside the cell because the phagocytic cells are destroyed. Many other yeasts, foreign bodies, artificial pollution, parasites and other yeast types that may resemble the bacteria should be distinguished.

(2) Fungal culture: The sputum of primary lung infection is most suitable for the isolation of the bacteria. The first sputum after the patients mouth is taken from the morning, and the purulent or bloody sputum is preferred, and the sputum is directly inoculated into the blood. Cultured on agar or sandcast agar at 25 ° C, the culture should be carefully examined, sometimes easily contaminated by other contaminating bacteria and Candida albicans. At this time, Smith and Goodman modified medium - yeast extract containing ammonia hydroxide can be used. Medium, which inhibits many bacteria, yeasts, and saprophytic fungi, and neutralizes the acid produced by yeast.

Other pathological materials such as biopsy specimens, sternal punctures, etc. can be planted on blood agar or sand castle agar, sealed with tape, placed in a plastic bag to prevent the medium from drying out, cultured for 6 to 12 weeks, when there is hyphae It should be identified on the blood agar. The colony is initially spherical, brain-shaped, pink to reddish brown, and sometimes can be turned into white to light brown filamentous colonies. At this time, it is difficult to distinguish it from dermatitis buds and many other fungi. It is helped by the large conidia with spines and transformed into yeast type. The biphasic colonies of this strain are mainly expressed in fungal colonies. The microscopic examination has slenderly separated hyphae and a few rounds with a diameter of 2~3m. Small conidia of shape or pear shape, and round or pear-shaped thick wall of 8-15 m in diameter, with spiny gear-like spores, located on both sides of the hyphae or the top of the spore handle, which has appreciative significance for the bacteria .

3. Serum test

(1) Screening test: Early latex agglutination test is often positive. Immunodiffusion method can help distinguish active or inactive lesions. Similar to latex agglutination test, it is often positive after 2 to 5 weeks of symptoms, and fluorescein can also be used. Label antibody test.

(2) Confirmation test and prognosis estimation test: The complement fixation test should be positive after other tests are positive for more than 6 weeks, and the titer of 1:32 is meaningful, but sometimes it is 1:8 or 1:16 in the active disease stage. That is meaningful, it should be used for gradient dilution. In general, the complement fixation test combined with the intradermal histoplasmin test is most valuable for the diagnosis and estimation of prognosis.

4. Histopathology: disseminated patients showed chronic granuloma changes, rarely purulent, caseous necrosis, tissue cells, lymphocyte infiltration, and epithelioid cells, giant cells and fibroblasts, neutrophils Less, spores are round or oval, with a capsule, 3m in size, parasitic in tissue cells or macrophages, HE, GMS, PAS or Gram stains all show intracellular spores, but must be with other yeasts, Identification of yeast-like fungi and protozoa, especially Penicillium marneffei.

Diagnosis and identification of capsular histoplasmosis

The disease should be distinguished from tuberculosis in all stages, mainly by culture and appropriate serological examination. The acute phase of primary histoplasmosis should be associated with other fungi, viruses and bacterial, lipidoid lungs. Identification of lesions and diffuse interstitial pulmonary fibrosis, acute disseminated histoplasmosis with splenomegaly, lymphadenopathy, anemia and leukopenia, such as visceral leishmaniasis and lymphoma, should be noted It should also be differentiated from infectious mononucleosis, Marneffe's blue mold, brucellosis, dysentery, Gaucher disease, etc. When there is skin and skin mucosal damage, it should be associated with tumor, sporotrichosis. , syphilis, toxoplasmosis, bacterial cellulitis, skin tuberculosis or other systemic fungal infections.

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