Overview of Coccidioidomycosis
Coccidioidomycosis is a fungal disease of the lungs or other organs caused by Coccidioides immitis. The lungs are the portal of invasion for Coccidioides immitis and the most frequently affected organ, and are clinically categorized as primary and progressive. Primary is an acute, self-limiting respiratory infection; progressive is a chronic, often fatal systemic infection.
Etiology
Coccidioides vulgaris is a biphasic fungus that is arbuscular mycelium in nature and forms small spherical spores in the host, which reproduce by forming endospore in mature spheres. The fungus is more tolerant to dryness, sunlight, ultraviolet light, more sensitive to formaldehyde generally 60 ℃, 1 hour can kill.
Symptoms
60% of patients present asymptomatic subclinical passages, only found in the coccidioidomycosis skin test examination. 40% of patients with varying clinical manifestations are mainly the following types:
1. Primary pulmonary coccidioidomycosis
Flu-like symptoms with dry cough and occasional bloody sputum appear 10 to 16 days after infection. Chest pain is often present. Chest signs are often negative. 20% of patients have conjunctivitis, and allergic skin lesions such as erythema deformans and erythema nodosum may be accompanied by multiple plasma membrane infections (pleurisy, pericarditis, arthritis). The course of the disease is self-limiting, with symptoms subsiding within 6 to 8 weeks. The initial stage of infection is prone to clinical fungemia, but rarely causes destructive extrapulmonary lesions, which are mainly seen in the skin, joints, bones and meninges.
X-ray manifestations include enlarged hilar lymph nodes pleural reactions and pleural effusions Intrapulmonary nodular lesions resolve within 6 to 8 weeks of onset. Rarely, residual lung abnormalities are commonly seen as pulmonary coccidioidomycosis nodules and cavities.
2. Chronic progressive Coccidioides immitis pneumonia.
After 8 weeks of primary infection, lung lesions persist and progressively worsen with persistent low-grade fever, cough, anorexia, weight loss, and hemoptysis in some patients. The course of the disease is slow and prolonged, lasting from months to years.
X-ray manifestations of lung segments or lobes of the infiltration shadow multiple cavities and fibrous nodular foci most of the cavity for 2 ~ 4cm, a few for the large cavity (> 6cm), typically thin-walled, no obvious inflammatory infiltrate around, to the two upper lungs are more common coccidioidomycosis nodules are usually no calcification, doubling time is more than 1 year.
3. Coccidioidomycosis with cornified lungs
This type is a serious complication of primary pneumocystis, in which the pathogen spreads to the whole lung field and other organs outside the lungs through bloodstream. It often occurs early in the course of primary pneumocystis, but can also be a late complication of a chronic progressive disease that can rapidly progress to respiratory failure in immunosuppressed individuals and in those with severe underlying disease and susceptible races, with clinical and radiographic manifestations resembling those of an immunocompromised host with tuberculosis of the cornified lungs. Hematogenous spread may involve the skin, joints, lymph nodes, meninges, liver, spleen and other organs.
Examination
(I) Laboratory tests
1. Peripheral blood picture
Peripheral blood leukocyte count may increase, primary Coccidioides immitis often have increased blood eosinophils, the onset of the second to third week is the most obvious
2. Coccidioides skin test
90% ~ 95% of patients with primary infection 4 weeks after the skin test reaction is positive with coccidioidomycin intradermal test, the dose of 0.1 ml, the skin redness range ≥ 5mm is positive, can last 24 ~ 48 hours. However, previously infected patients can also be persistently positive. Patients with hematogenous dissemination can be negative.
3. Pathogenetic examination
Sputum, puncture fluid, fiberscope specimen, pleural biopsy specimen, the smear treated with potassium hydroxide can be seen as round, thick-walled, endospore-containing spheres, which can be cultured on glucose peptone agar for 1 week with mycelial colony growth. A positive culture for Coccidioides pulmonicus is of special significance for the diagnosis. The positive rate of sputum culture is 40%～60%, and the positive rate of fiberoptic specimen is higher.
4. Serologic examination
Serologic methods for detecting antibodies to Coccidioides are rarely false-positive, and the sensitivity of latex agglutination test reaches 90%, which is often used for initial screening. Complement binding test detects IgG antibody, 50% of patients are positive in the 4th week of infection, 90% of patients are positive in the 8th week, and disappear in 6-8 months. Antibody titers correlate with disease severity. Tube precipitation test for IgM antibody is positive in 50% of patients in the first week of infection and is suitable for early diagnosis.
5. Gene probe diagnosis
Specific gene probes have been applied to the rapid diagnosis of Coccidioidomycosis and the results can be obtained in 48h.
(ii) Other auxiliary tests
Primary pulmonary coccidioidomycosis X-ray manifestations of pulmonary hilar lymph node enlargement, pleural reaction and pleural effusion. Nodular lesions in the lungs may subside within 6 to 8 weeks of onset. Rarely, residual lung abnormalities commonly remain as pulmonary Coccidioides nodules and cavities.
Chronic progressive coccidioidomycosis pneumonia radiographically shows infiltrative shadows in lung segments or lobes, multiple cavities and fibrous nodular foci. Most cavities are 2 to 4 cm, and a few are large (>6 cm), typically thin-walled, with no significant surrounding inflammatory infiltrate, and are more common in the two upper lungs.
The clinical and radiographic manifestations of Coccidioidomycosis militaris resemble those of tuberculosis militaris.
Diagnosis
The disease should be suspected in people with respiratory infections in endemic areas, and the coccidioidomycin test should be performed routinely. The diagnosis can be made on the basis of the history of exposure to the endemic area, clinical manifestations and X-ray features, immunologic examination, and the finding of the characteristic spheres of Coccidioides immitis on smear or culture can confirm the diagnosis.
Differential diagnosis
The disease should be differentiated from bronchitis, pneumonia, tuberculosis, and lung tumors.
Complications
There are 3 potential complications of Pneumocystis carinii:
1. secondary bacterial or other fungal infections.
2. Rupture of the cavity.
3. fatal hemoptysis.
Treatment.
Primary pulmonary coccidioidomycosis usually does not require treatment. Oral ketoconazole may be given to immunocompromised patients with mild disease, and amphotericin B or ketoconazole may be given to patients with severe prolonged symptoms or high risk factors for dissemination to prevent dissemination and chronicity. Chronic progressive Coccidioides immitis pneumonia, with amphotericin B. Ketoconazole can improve the symptoms but may recur after discontinuation of the drug, depending on the clinical response and toxicity, the course of treatment for 3 to 6 months or longer. Fluconazole is also effective. In patients with severe, disseminated disease, combination therapy can help improve the condition available transfer factor (TF), etc. Surgery is indicated for symptomatic cavities of ballooning spores lasting more than 6 months with recurrent hemoptysis secondary to infection or in high-risk patients (diabetes mellitus).