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Anthracosis is black pigment discoloration of bronchi and can cause bronchial destruction and deformity (anthracofibrosis)1-11 (Fig. 1). Anthracosis is considered as a benign bronchial finding during bronchoscopy, and it is a rare finding in developed countries. There is anecdotal evidence that this disease is increasing in prevalence in Iran. This disease is a major cause of obstruction in large bronchi and can result in severe respiratory symptoms such as cough, dyspnea, and a tendency for infections. Histopathology findings are anthracotic granules, inside and outside of macrophages, and edema and scattered inflammatory cells. Anthracosis is usually thought to be a condition of coal miners and occasionally city-dwellers. In some experience, it is not only associated with environmental exposure, but also with smoking.2 Infectious diseases10 and malignancies3 were implicated as background of anthracosis. Active tuberculosis (TB), for unknown reasons, was present along with anthracosis without granuloma formation. The objective of this study was to study the relationship between anthracosis and these predisposing factors.
MATERIALS AND METHODS
A prospective, case-control study was performed in tertiary Mashhad University hospitals. All patients who underwent flexible bronchoscopy for various indications during the year of 2003 were considered for this study. A sample size of 190 was calculated as sufficient for a 0.05 alpha error and 80% potency on the basis of prevalence of anthracosis (8%) and 99% confidence level.1 Demographic data and important clinical findings were recorded. During bronchoscopy, special attention was given to anthracotic plaque, deformity, infiltration, exophytic lesion, and standard bronchoalveolar lavage. Biopsy was taken for histopathology examination when malignancy or granulomatous disease was suspected during bronchoscopy. In all patients, bronchial smear were examined for acid-fast bacilli (AFB) and culture.
Standard bronchoalveolar lavage (BAL) was performed in all patients. Biopsy was taken for histopathology examination when malignancy or granulomatous disease was suspected during bronchoscopy. In all patients, cytology specimens of BAL were examined for macrophage containing anthracotic granule and bronchial smear for AFB and culture (Levinstein Johnson media). Patients with 3 or 4 positive smears for AFB or positive culture for Mycobacterium tuberculosis and caseous necrotizing granuloma in biopsy were considered to have tuberculosis.
This study was approved by the ethics committee of the research department of the medical school of Islamic Azad University of Mashhad. Written consent was provided by all patients. Pearson chi-square, odd ratio, Fisher exact test, and t test with 0.05 errors and 95% confidence interval were used for statistical analysis.
One hundred eighty-nine patients underwent bronchoscopy (95 male and 94 female), aged 10 to 85 years (average age, 60 years; standard deviation, 16). Simple plaque of anthracosis was found in 21% (41 of 188) and anthracofibrosis in 11.7% (22 of 188). Of all patients, 54.5% with anthracofibrosis were female.
Gross bronchoscopic findings in simple anthracosis included a patchy flat black discoloration of large bronchi and circular contiguous black discoloration in small visible bronchi. By contrast, anthracofibrosis made bronchi occluded with edema and infiltration of submucosa, but the surface of the epithelium was shiny without ulceration (Fig. 1). Sputum smear showed macrophage containing anthracotic granule in 71% (129 of 181).
Most male patients were farmers (46%) and manual workers (27%). For female patients, 91% were housewives. No correlation between occupational exposure to dust and 2 kinds of anthracosis (anthracotic plaque and anthracofibrosis) was present (chi square = 0.4, P = 0.19, and chi square = 0.13, P = 0.36, respectively). Also, there was no correlation between tuberculosis and occupation (P = 0.48).
The main presenting complaint of patients who had bronchoscopy was cough (92%), dyspnea (69%), and hemoptysis (28%). None of these symptoms had statistical correlation with the type of anthracosis (Table 1).
Smoking of cigarettes, a waterpipe, or a pipe in this study was considered a positive smoking history. Smoking was more prevalent in male patients and inversely related to tuberculosis (chi square = 5.5, P = 0.018). Smoking status was not related to major symptoms or type of anthracosis. Among anthracofibrotic patients, 81% were nonsmokers (Table 2).
Relation of Anthracosis and Tuberculosis
Active tuberculosis was found in 30% of patients (52 of 172) of whom 22 had positive sputum smears; 42 of 163 (25%) had positive cultures. Tuberculosis was confirmed in 18 of 102 (17%) patients only with histopathology. Accuracy of AFB smear and culture is shown in Table 3.
The incidence of tuberculosis in 2 forms of anthracosis presentation is shown in Table 4. Twenty-one percent of patients with anthracosis had positive histopathology findings for tuberculosis. There was no statistically significant correlation between anthracofibrosis and tuberculosis (P = 0.09).
Relation of Anthracosis and Bronchogenic Carcinoma
The principle finding of bronchoscopy was exophytic lesion in 40% (75 of 188). In patients who underwent biopsy, 24 patients had malignancy in histopathology (21%, 24 out of 110 biopsies). In 40 patients with simple anthracotic plaque and 22 anthracofibrosis patients, only 2 and 1 patients, respectively, were proved to have bronchogenic carcinoma that was not statistically significant (Table 4). Types of cancer in patients with simple plaque of anthracosis were squamous cell carcinoma and undifferentiated carcinoma.
Anthracosis is black pigment discoloration of bronchi, and when it causes bronchial destruction and deformity, it is called anthracofibrosis10 (Fig. 1). Anthracosis is an ancient condition and was initially reported in mummies.4,5 Four decades ago, this condition was reported in pneumoconiosis patients.6 Since then, frequency of the condition has decreased in developed countries, yet it is still prevalent in certain parts of the world.9 Most authors considered this disease as one of the complications of occupational diseases.7-10 Chung et al.9 Towhidi et al,1 and Aslani et al10 reported anthracofibrosis in 3%, 8%, and 10% of routine bronchoscopies, respectively. In our study, we found simple anthracosis in 21% of routine bronchoscopies. Anthracofibrosis can distort bronchial lumen and cause clinical problems, and is the most important form of pulmonary anthracosis. In addition to the lung, anthracosis may involve lymphoreticular organs and liver.11-14 For elucidation of origin of anthracosis, Tanaka et al15 performed special bronchoscopic study in small bronchi and concluded that peripheral airways are the initial site of anthracotic granule production.
Because many patients with anthracosis were not exposed to air dust at work, other investigators studied other possible causes of anthracosis. Muliez et al2 reported 3 patients with anthracosis that proved to have Mica in lung biopsy material. They concluded that anthracotic plaque might be associated with domestic pollution. Kato and Kawaga16 examined the effect of polluted roadside air on the pathogenesis of chronic respiratory disease (goblet cell proliferation and inflammatory cell accumulation) and anthracosis on rats during a 60-week trial. Their findings suggested that the effect of roadside air on the respiratory tissue in rats might not be as severe as would be expected under this experimental condition.
To characterize the relationship between background anthracosis and pulmonary carcinogenesis, some investigators studied the association of anthracosis and lung cancers,17,18 especially to adenocarcionoma.19-21 Wang and coworkers3 examined surgically resected tissues of 66 cases with pulmonary adenocarcinoma. They concluded that adenocarcinoma developing in heavily anthracotic lungs readily progresses to an advanced stage or that adenocarcinoma with a less favorable prognosis tends to develop in severely anthracotic lungs.19
Chung et al10 studied 908 patients and found tuberculosis in 61% of patients with anthracofibrosis, and suggested that infective etiology is strongly considered for severe anthracosis.
In this study, we studied clinical characteristics of the patients showing anthracosis and its association with tuberculosis, lung cancers, and occupational exposure to dusts. According to our results, anthracotic plaque is a prevalent finding in bronchoscopy (21%), in comparison to other countries such as Korea where this disease is reported to be present in 3.7% of 908 routine bronchoscopies.10 Female gender was more prevalent in those studies by Aslani et al, Chung et al, and Towhidi et al1,10,11 (54.5%, 68%, and 71%, respectively). Amoli9 reported 10 nonsmoker elderly housewives with chronic bronchial anthracotic plaque with a history of prolonged exposure to smoke over many years while baking household rustic bread inside their dwelling. A recent report by Aslani11 showed this kind of exposure to be present in 30% of cases. In Chung,10 Aslani,11 and our study, 71%, 93%, and 81% of patients, respectively, with anthracofibrosis were nonsmokers, so smoking habit was not the predominant risk factor. In our patients, occupational exposure to dusts was not significantly correlated with anthracosis. Moreover, although most of the patients lived in the countryside and therefore were less exposed to roadside pollutions, this was not shown to be a risk factor either. We studied infectious etiology of anthracosis, and particularly tuberculosis, but we did not find this as prevalent as reported previously.1-10 Interestingly, biopsy of patients with anthracofibrosis proved to have tuberculosis did not show typical granuloma formation, and the reason for this is not known. Results of research about the presence of Mycobacterium tuberculosis with polymerase chain reaction methods in our center will be released in the near future. Effect of domestic exposure to mineral dust, smoke from incomplete burning of herbal material, and diesel exhaust on the anthracosis should be investigated in the future.
The authors thank Mostafa Alamee and Esmaeel Zareh in the bronchoscopy department of Ghaem Hospital, Mashhad, Iran.
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