OVERVIEW
Allergic bronchopulmonary aspergillosis (ABPA), also known as allergic bronchopulmonary aspergillosis, is one of the most common and characteristic diseases of allergic bronchial mycoses, which was firstly reported in Britain in 1952. Its pathogenic Aspergillus fumigatus is the most common, Aspergillus flavus, Aspergillus oryzae and Aspergillus terreus can be seen occasionally. The main symptoms in the acute stage are wheezing, hemoptysis, pus sputum, fever, chest pain and coughing up brown sputum.
Etiology
Most cases of ABPA are due to a high degree of hypersensitivity to Aspergillus, especially Aspergillus fumigatus, which is the most common, and inhalation of high concentrations of Aspergillus fumigatus spores by atopic individuals who are sensitive to Aspergillus is the main pathway of the disease.
Symptoms
1. Typical manifestations
In the acute stage, the main symptoms include wheezing, hemoptysis, pus and sputum, fever, chest pain and coughing up brown sputum. The majority of hemoptysis is sputum blood, but a few patients have a large amount of hemoptysis. Symptoms in the acute phase are of long duration, often requiring six months of hormone therapy to subside, with a few cases evolving into a hormone-dependent phase. The frequency of acute exacerbations has been reported differently due to the different definitions of the acute phase. nearly half of the patients with ABPA need long-term local inhalation or systemic application of hormones, even though the symptoms of asthma are milder.
2. Atypical manifestations
Occasionally, ABPA coexists with Aspergillus globulus.ABPA can also have extrapulmonary dissemination in a very small number of patients, such as cerebral invasion, cerebrospinal fluid lymphocytosis, pleural effusion.
3.The clinical course of ABPA is divided into 5 stages.
Not every patient has to go through a clinical course of 5 stages.
Stage I (acute stage) Mainly characterized by episodic symptoms such as wheezing, fever, weight loss, etc. Significantly elevated IgE levels, eosinophilia, infiltrating shadows in the lungs, positive serum IgE-Af and IgG-Af.
Stage II (remission) Symptoms are usually controlled by bronchodilators and inhaled glucocorticoids, X-ray chest radiographs are normal, serum IgE-Af and IgG-Af are not significantly elevated or are mildly elevated, serum IgE levels are reduced but not returned to normal, and there is no eosinophilia. Complete remission is defined as a 35% to 50% decrease in serum IgE within 6 to 12 weeks of treatment, or no exacerbation of the disease for more than 3 months after discontinuing oral glucocorticoid therapy for 6 to 9 months.
Stage III (exacerbation) Most patients have acute exacerbations, and some patients have asymptomatic relapses with only a twofold increase in total serum IgE or new infiltrates in the lungs, so this stage requires close monitoring.
Stage IV (hormone-dependent stage) Manifests hormone-dependent asthma, asthma symptoms must be controlled by oral glucocorticoids, asthma worsens when hormones are reduced, and it is difficult to stop the medication even if the asthma resolves. Serum IgE levels are elevated or normal. Usually there are no lung infiltrating shadows on X-ray, but a few patients show diversity on chest radiographs, which may be accompanied by central bronchiectasis. The vast majority of cases are diagnosed in this stage.
Stage V (fibrosis stage) Patients often have extensive bronchiectasis, pulmonary fibrosis, pulmonary hypertension, fixed airflow obstruction, and severe irreversible impairment of lung function, which may include chest tightness, shortness of breath, dyspnea, cyanosis, and respiratory failure, and pestle and mortar fingers may be seen. Patients may have a poor prognosis with serologic tests with or without active stage manifestations.
Examination
Elevated total serum IgE, the cut-off value used for elevated total serum IgE in current diagnostic criteria is generally 1000 IU/ml, and the use of an alternative cut-off value of 1000ug/L (equivalent to 417 IU/ml) may lead to an overdiagnosis of ABPA, a positive antibody to treponemal precipitin, and elevated serum-specific IgE and IgG antibodies. Peripheral blood eosinophils are increased.
The nonspecific imaging manifestation of ABPA is recurrent, migrating pulmonary infiltrative shadows, with 80% to 90% of patients presenting with varying degrees of pulmonary infiltrates, ranging from small to large sheets of whole lobe solid lesions, mostly appearing at some point in the course of the disease, and not always associated with acute symptoms. 30% to 40% of patients present with generalized pulmonary hyperinflation or decreased lung volume.
The specific imaging manifestations of ABPA are central bronchial dilatation mainly in the upper lobes, bronchial wall thickening, dilatation, and double-track sign and ring sign on CT scan, and obstruction of the bronchial tubes by secretory sputum plugs may be characterized by strip, branch, or toothpaste or fingerprint-like shadows. Mucus embeddedness is also a common and characteristic X-ray sign of ABPA, 37% to 65% of patients have X-ray evidence of mucus embeddedness at some time during the course of the disease, accounting for nearly one-third of all transient lesions. typical manifestations are 2-3cm long, 5-8mm straight strips or finger-like bifurcation of opacity shadows ranging from ground-glass to solid shadows, as well as sputum thrombus due to pulmonary atelectasis and so on, and in the late stage can appear Emphysema and fibrosis can be seen in advanced stage. Imaging changes are more common in the upper lobes of the lung, which are two to three times more common than the lower lobes.
Lung function impairment in patients with ABPA includes abnormalities in lung ventilation and gas exchange function, depending mainly on the degree of disease activity. Some degree of reversible obstructive ventilatory dysfunction is most common. Chronic ABPA patients with advanced pulmonary fibrosis may present with restrictive ventilatory dysfunction, diffusion impairment, and fixed airflow limitation. It has been shown that reversible airway obstruction with reduced diffusion in ABPA parallels lung volume reduction. As the disease progresses, irreversible airway obstruction and varying degrees of pulmonary fibrosis often occur, and the impairment of lung function further worsens.
Diagnosis
1. The initial diagnosis of ABPA is based on Rosenberg Patterson’s diagnostic criteria.
(1) Main criteria ① bronchial asthma; ② presence or previous pulmonary infiltrates; ③ central bronchiectasis; ④ peripheral blood eosinophilia (1000/mm3); ⑤ Aspergillus fumigatus allergens rapid-onset skin test negative; ⑥ Aspergillus fumigatus allergens precipitating antibody positive; ⑦ serum anti-Aspergillus-specific IgE, IgG antibody increased; ⑧ serum total IgE concentration increased (>1000ug/l). (8) Increased serum total IgE concentration (>1000ug/l).
(2) Secondary diagnostic criteria include ① repeated sputum smear or Aspergillus culture positive; ② cough brown sputum plug; ③ Aspergillus allergen delayed skin reaction positive.
2. 1997, Greenberger proposed the minimum diagnostic criteria of ABPA.
① asthma; ② skin test Aspergillus antigen positive rapid reaction; ③ serum total IgE increased; ④ serum anti-smokers Aspergillus IgE increased and (or) IgG level increased; ⑤ current or previous pulmonary infiltrates diagnosed as ABPA-S; ⑥ combined with central bronchiectasis diagnosed as ABPA-CB.
3. Diagnosis of ABPA in the Guidelines for the Diagnosis and Treatment of Aspergillosis established by the Infectious Society of America in 2008
(1) There are seven major criteria: (1) bronchial obstructive symptomatic episodes (asthma); (2) peripheral blood eosinophilia; (3) positive rapid-onset skin test for Aspergillus allergens; (4) positive serum Aspergillus allergens precipitating antibodies; (5) increased serum total IgE concentration; (6) the presence of, or a previous history of, infiltrating shadows in the lungs on pulmonary imaging; and (7) centralized bronchiectasis.
(2) Secondary diagnostic criteria include ① repeated finding of Aspergillus in sputum smears and/or cultures; ② history of coughing up brown mucus plugs or plaques; ③ increased serum Aspergillus-specific IgE antibodies; and ④ a positive Aspergillus allergen delayed skin test.
Differential diagnosis
It needs to be differentiated from asthma, chronic eosinophilic pneumonia, Churg-Strauss syndrome, and tuberculosis. In ABPA presenting with pulmonary infiltrates, the increase in peripheral blood eosinophils and the elevation of total IgE (mean 2000-14000ng/ml) are quite significant, and can be clearly differentiated from patients with Aspergillus skin test-positive asthma.
Treatment
Glucocorticoid therapy relieves and eliminates symptoms during acute exacerbations and prevents permanent damage such as bronchiectasis, irreversible airway obstruction and pulmonary fibrosis. Prednisone is recommended, and the dosage is discretionary based on clinical symptoms, radiographic findings, and total IgE levels.