Overview of Aspergillosis
The main causative agent of pulmonary aspergillosis is Aspergillus fumigatus, and some of the causative agents are Aspergillus flavus, Aspergillus clavatus, Aspergillus terreus, Aspergillus niger, Aspergillus tectonicus and Aspergillus floridus. Most of the disease is secondary infection, and the primary is rare. The disease is clinically categorized into three types: Aspergillus ball, allergic bronchopulmonary aspergillosis (ABPA) and invasive pulmonary aspergillosis (IPA).
Etiology
The most common type is Aspergillus ball. Aspergillus bacteria often parasitize cavities formed by chronic lung diseases such as tuberculosis, lung cancer, bronchopulmonary cysts and tuberculosis. The walls of the cavity and the surrounding portions of the lung tissue are destroyed, and the alveoli are filled with eosinophilic amorphous material, red blood cells, yellow-brown globules, septate branching mycelium, chronic inflammatory cell infiltration, and proliferating small arterioles and venules, which are verrucous and dilated, with no invasion of mycelium.ABPA is caused by the combined effects of type I and type III metaplasia. Inhaled short-chained Aspergillus spores are present in bronchial secretory mucus and form mycelium; their antigens sensitize with IgE to specifically bind to mast cells, releasing mediators that cause bronchospasm. In addition, Aspergillus antigens bind to IgG antibodies to form immune complexes that lead to bronchial destruction, dilatation, and pulmonary fibrosis with the involvement of complement.IPA is seen in patients with chronic wasting disease, reduced immune function, and dysbiosis. Parasitic Aspergillus in the upper respiratory tract invades the lung tissue, forming multiple abscesses or granulomas with small arterial emboli at the margins of the lesions. Invasion of Aspergillus through the pulmonary vasculature leads to hematogenous dissemination, which may involve other organs of the body.
Symptoms
Patients with Aspergillus may present with cough and hemoptysis, with unremarkable systemic symptoms.
Patients with ABPA are often atopic, with recurrent episodes of wheezing, coughing, coughing up brown sputum clots, hemoptysis, and fever. Both lungs may be covered with rales, and the infiltrated lungs have fine wet rales. The intradermal test of the Aspergillus leachate may show a biphasic reaction: type I allergic reaction in the test 15-20 minutes later, the appearance of the wind and redness of the reaction, 0.5-2 hours subside; type III allergic reaction in the 4-10 hours again observed in the skin test localized Arthus reaction, 24-36 hours to subside.
Severe disease is mostly in patients with IPA, manifested by fever, cough, cough purulent sputum, hemoptysis, chest pain, dyspnea, as well as signs and symptoms caused by dissemination to other organs. Dry and wet rales are present on lung auscultation.
Examination
1. Chest X-ray examination
Allergic type shows increased lung texture or lung infiltration; invasive type shows bronchopneumonia changes. Aspergillus ball is often located in the cavity, the cavity is half-moon shaped air shadow, the ball seems to be pendulum-like with the change of body position and move.
2. Tests
(1) Sputum smear microscopy shows mycelium and spores;
(2) Repeated positive sputum culture is helpful for diagnosis;
(3) A large number of eosinophils can be seen in the sputum of allergic patients, and the total blood IgE is increased;
(4) Positive Aspergillus antigen skin test and serum precipitation test are helpful for diagnosis.
Diagnosis
Clinical episodes of bronchial asthma, peripheral blood eosinophilia, elevated serum IgE, lung infiltration foci on X-ray, Aspergillus mycelium on smear of secretions aspirated by fiberoptic microscopy, or Aspergillus growth in culture, can be diagnosed as metaplastic bronchopulmonary aspergillosis. Fluoroscopic localization and transfibrillar lung biopsy are valuable in confirming the diagnosis of Aspergillus ball and invasive pulmonary aspergillosis.
Differential diagnosis
1. Bacterial pneumonia
There are symptoms such as high fever, cough, sputum, shortness of breath, chest pain, etc., wet rales in the lungs, elevated white blood cell count, and flocculent infiltrating shadows on X-ray, which need to be determined by isolation of the causative organisms from sputum specimens, pleural fluid or blood.
2. Viral pneumonia
Viral pneumonia first appears as an upper respiratory tract infection, spreading downward to cause lung inflammation. Bacterial infection may be induced. Diagnosis is based on isolation of virus from throat swabs and sputum and determination of serum-specific antibodies.
3. Tuberculosis
Mostly seen in young patients, with symptoms such as hot flashes, night sweats, clinical manifestations of irritating dry cough, cough sputum, cough worsened after the formation of cavities, sputum increased, may be accompanied by hemoptysis. According to chest X-ray examination, sputum or other specimens found in tuberculosis bacteria.
4. Lung abscess
The onset of the disease is rapid, and the clinical manifestations include high fever, cough, coughing up a large amount of purulent sputum or pus and blood sputum, chest pain and other symptoms. The white blood cell and neutrophil counts are increased, and the X-ray examination reveals pus cavities and fluid planes.
5. Bronchial dilatation
Bronchiectasis is commonly seen in young adults, with chronic cough and large amount of purulent sputum, and history of measles, whooping cough, bronchopneumonia, etc. Unilateral or bilateral coarse and disorganized and curly shadows can be seen on X-ray chest film. High-resolution CT and bronchial iodine-oil angiography can confirm the diagnosis.
Treatment
Aspergillus ball is usually ineffective with antifungal medications and should be treated early with surgery.
Patients with metachronous reactive bronchopulmonary aspergillosis are treated with antifungal drugs, which are effective against endobronchial aspergillosis but are prone to recurrence. Corticosteroids are currently the most effective drugs for the treatment of this disease, which can inhibit the occurrence of metaplasia and reduce sputum, which is not conducive to Aspergillus planting. Oral prednisone helps lung infiltration absorption, can also be combined with diamycin B, commonly used flumethasone and diamycin B added to saline nebulized inhalation. For recalcitrant patients, bronchoscopic irrigation can be performed to aspirate secretions and maintain airway patency to improve the efficacy of drugs.
IPA patients are treated with antifungal drugs. Amphotericin B is preferred, and can be combined with rifampicin for oral administration, which has a synergistic effect. Flucytosine can also be applied. Itraconazole has strong antifungal activity and is definitely effective against Aspergillus. For patients with persistent, recurrent, invasive pulmonary aspergillosis, partial lung resection can be performed if the lesion is limited.
Prevention
1. In the suspected Aspergillus contaminated environment or fungal laboratory should be well protected, wear protective masks to avoid inhalation of germs, resulting in lung infection.
2. Strengthen protective measures, in dusty places, need to wear masks, timely treatment of eye and skin trauma, eliminate or reduce various triggering factors, and actively treat chronic diseases.