Virendra Singh describes for SIIC his article published in Lung India 32(2):102-106, March 2015

Jaipur, India (special for SIIC)
Black discoloration of the trachea is found in a number of conditions such as: agyria (deposition of silver), melanosis, charcoal inhalation, alkaptonuria and anthracosis. The most common amongst these is anthracosis. Deposition of carbon and silica particles in the airway mucosa leads to an abnormally black pigmented area during bronchoscopy and this is called as anthracosis. Airway narrowing may be associated with this pigmentation and the disorder is then called as anthracofibrosis. The disease was first identified in 1951 and the term was coined much later in 1998 by Chung et al. Recently, there has been controversy regarding the term anthracofibrosis. Many authors propagate the term anthracostenosis, because it better describes the clinical entity visualized on bronchoscopy. Anthracofibrosis, on the other hand is a pathological diagnosis.

We studied 30 cases with anthracosis evident on bronchoscopy and 53 controls with no anthracosis on bronchoscopy matched according to age, gender and smoking habits. The study was conducted at SMS hospital, Jaipur, India; a country where tuberculosis is quite widespread. Aim of the study was to study the association of anthracosis with other pulmonary disease and other exposures.

The condition commonly affects middle aged to elderly population with mean age of presentation as 59.4 ± 12.7 years. The condition affects women (16%) more as compared to men (7%) as was evident in our study also. The common presenting clinical symptoms of anthracosis are cough, difficulty in breathing, coughing out blood and tiredness. We found that 20% of our anthracosis patients had history of stone mining which was significantly more as compared to the control group. Two theories have been proposed to explain this association. First silica leads to macrophage dysfunction which inturn leads to impaired clearance of inhaled particles and deposition of these in the airway mucosa. The second theory is that silicosis predisposes to tuberculosis and which inturn is associated with anthracosis.

Biomass fuel smoke has been associated with the development of this disorder and the entity was also called the hut lung earlier. However, in our study we did not find any significant difference in the hours of exposure to biomass smoke amongst the cases and controls (p > 0.05).

Tuberculosis both active and old healed disease was 7 times more common in our patients with anthracosis as compared to the controls. Inhaled particles such as carbon and silica get deposited in the airways and are subsequently cleared by the lymphatics to the draining lymph nodes. Tubercular infection of these nodes may cause their rupture into the adjoining bronchial mucosa leading to the black pigmentation. Another theory is that silica pigmentation leads to altered immune response and predisposition to infections such as tuberculosis.

Malignancy and pneumonia were less commonly seen in patients with anthracosis. Previous work with regards to the association have reported contrary findings. It has been postulated that airway narrowing associated with anthracosis will lead to impaired clearance of secretions and may lead to bronchopneumonia. However our study could not substantiate this theory.

Computed tomography (CT) chest revealed that fibrosis was more common in the cases as compared to controls. Tuberculosis leads to fibrosis and lymphademopathy and thus both were common in the cases.

The condition commonly affects the upper lobes of the lung. Previous studies have shown either a upper lobe or middle lobe preponderant disease pattern. The upper lobe preponderance can also be correlated with the fact that pulmonary tuberculosis (PTB) generally involves the upper lobes and PTB is also more common in cases of anthracosis. We performed bronchoscopy in our cases and controls, but with the advent of newer technology such as endobronchial ultrasound guided fine needle aspiration cytology (EBUS-FNAC) can be done to access the lymph nodes directly.

Clinical implications of anthracosis may be profound and thus this condition should not be ignored. Huh et al had previously reported that an undiagnosed patient with anthracofibrosis was taken up for surgery and the post operative course was complicated by hemorrhage. The bleeding arose from trauma induced by a suction catheter which was inserted to remove excess secretions. Exploration of the bleeding site via bronchoscopy revealed black pigmentation with severe narrowing of the right main bronchus. The anaesthesist should be aware of such complications since they can be avoided by being vigilant. Use of laryngeal mask airway, avoidance of suction catheter and use of anticholinergic agents to prevent excess secretions are some of the maneuvers to avoid hemorrhage in such cases. Another important clinical implication is the fact that anthracofibrosis shows hypermetabolism on fluoro-deoxy-glucose positron emission tomography (FDG-PET) and can be confused with malignancy.

To conclude, we found that anthracosis is common in females, with history of old or active tuberculosis and fibrosis evident on CT chest. However we need larger prospective studies which include follow-up bronchoscopy to confirm our findings. Moreover the treatment strategies have to be studied as yet there are no current treatment guidelines for the same.