Rare presentation of endobronchial tuberculosis: A case series

Editorial

To the editor: Tuberculosis (TB) is a major global health problem. Endobronchial TB (EBTB) is defined as a tuberculous infection of the tracheobronchial tree with both microbial and histopathological evidence, with or without involvement of the lung parenchyma.^[1] It was first described by Richard Morton in 1698.^[2] EBTB is difficult to diagnose because the lesions may be undetectable on a routine chest radiograph, and sputum smear (Ziehl-Neelsen (ZN) stain) examination has a low diagnostic yield.

Although EBTB is a well-known disease, in this case series we describe rare manifestations of EBTB. We retrospectively reviewed the medical records of all patients diagnosed with EBTB at our tertiary medical centre from January 2023 to February 2024. A total of eight EBTB cases were identified during the study period, of which we selected three because of their atypical presentation. The study was approved by the institutional human ethics committee (ref. no. 25/107). In view of the retrospective nature of the study, informed consent was waived.

Case 1. A 24-year-old immunocompetent man, a non-smoker, presented with a month’s history of a productive cough, dysphagia with recurrent aspiration, and constitutional symptoms. The findings on clinical examination were unremarkable.

Contrast-enhanced computed tomography (CECT) of the chest revealed a fistulous communication between the trachea and anterior oesophagus at the T2 level (thoracic spine), as well as centrilobular nodules in the right lung. Sputum GeneXpert testing was positive for Mycobacterium tuberculosis (MTB) (rifampicin sensitive (Rif-S)). Upper gastrointestinal endoscopy (UGIE) and fibre-optic bronchoscopy (FOB) confirmed a tracheo-oesophageal fistula (TOF), 27 cm from the nares.

Anti-TB treatment (ATT) was initiated as per the National Tuberculosis Elimination Programme (NTEP) guidelines. A nasogastric tube was inserted to prevent aspiration and to provide enteral nutrition. After 4 months of ATT, surveillance UGIE confirmed that the TOF had closed.

Case 2. A 33-year-old immunocompetent woman, a non-smoker, presented with a history of a dry cough and breathlessness on exertion for the preceding 15 days. Clinical examination revealed drooping of the left shoulder and supraclavicular hollowing. On auscultation, coarse crepitations were audible in the left lung fields.

CECT of the chest showed complete collapse of the left lung, bronchiectasis, cavitary lesions, and mediastinal shift to the ipsilateral side. FOB revealed purulent secretions and stenosis of the left main bronchus. Bronchoalveolar lavage (BAL) samples were positive for MTB on GeneXpert (Rif-S), and drug-sensitive MTB growth was identified with a mycobacteria growth indicator tube culture (BACTEC MGIT 960; Becton Dickinson, USA). The patient was subsequently initiated on ATT and scheduled for endobronchial balloon dilatation. However, she has not yet returned for the procedure.

Case 3. A 55-year-old woman with well-controlled diabetes mellitus (glycated haemoglobin 6.6%) presented with a 7-day history of a dry cough and breathlessness. On auscultation, she had bilateral wheezing. A chest radiograph showed bilateral reticular opacities. CECT of the chest showed an endobronchial lesion in the right main bronchus, narrowing of the bronchus intermedius, and interstitial thickening on the right side involving the middle and lower lobes. As the CECT findings were consistent with a possible malignancy, FOB was performed to confirm the diagnosis. FOB showed a single tumorous growth in the right main bronchus, with caseation and fibrotic stenosis of the bronchus intermedius.

BAL samples were positive for MTB (Rif-S) on GeneXpert. Biopsies from the tumorous growth and endobronchial mucosa showed caseating granulomas, consistent with TB. The patient was initiated on ATT and is still being followed up.

Fig. 1.

Computed tomography scans (above) and bronchoscopy images (below). Case 1: tracheo-oesophageal fistula (arrow); case 2: complete obstruction of the left main bronchus (arrow) with post-obstructive bronchiectasis; case 3: tumorous growth in the right main bronchus (arrow) and narrowing of the bronchus intermedius.

The computed tomography scans and bronchoscopy images of the patients are shown in Fig. 1.

The incidence of EBTB ranges from 6% to 54%.^[3] It is more prevalent among females than males, possibly as a result of females’ smaller airway size and reduced sputum expectoration for cultural and aesthetic reasons.^[4] Previous studies have reported a bimodal age peak, with the first peak in the 2nd or 3rd decade and the second peak in old age.^[5] Similar patterns were observed in our case series. EBTB usually presents with nonspecific symptoms such as a cough (70 - 80%) or lung-specific symptoms such as wheezing, dyspnoea or haemoptysis (15 - 40%) due to endobronchial involvement. Sometimes symptoms related to the complications of EBTB may dominate the clinical picture, as in the first patient in our series, who had recurrent aspiration due to a TOF.

The chest radiograph is reported as normal in 10 - 20% of patients with EBTB. The most common radiological abnormalities are patchy parenchymal infiltrates, lobar collapse or hyperinflation, obstructive pneumonia or mucus impaction, depending on the extent of the endobronchial obstruction.^[6] CECT of the chest is more sensitive, showing centrilobular nodules, tree-in-bud lesions, mediastinal adenopathy or bronchial wall thickening. Chung and Lee^[7] classified EBTB into seven subtypes based on bronchoscopy findings. These subtypes are caseating, oedematous-hyperaemic, fibrostenotic, tumorous, granular, ulcerative, and nonspecific bronchitis. The most commonly encountered subtype of EBTB is oedematous-hyperaemic. ^[8] Sputum smear positivity (ZN stain) varies from 16% to 53%, and is high in the granular subtype. The possible reason for a low yield on ZN stain is mucus entrapment by proximal granulation tissue. A better diagnostic yield is obtained with GeneXpert testing.^[3] Bronchoscopy is an essential tool for early diagnosis and subtype identification. The yield of bronchial biopsies in EBTB ranges from 30% to 84%.^[3] Bronchial stenosis is a frequent and serious complication of EBTB, especially when it involves the large airways, as seen in the second patient in our series. The stenosis can lead to respiratory compromise secondary to collapse or bronchiectasis. TOF is an extremely rare complication of EBTB. The most likely cause of a TOF is rupture of a caseous peribronchial lymph node into the adjacent mediastinal structures, resulting in fistula formation.^[9] The mainstay of treatment is ATT, which includes rifampicin, isoniazid, pyrazinamide and ethambutol. All the patients in our case series had drug-sensitive TB and received treatment according to the NTEP. Management of complications includes advanced procedures such as balloon dilatation, stent insertion, laser therapy and cryotherapy.^[2,6] The management of TOF is unclear. There have only been a few reports of successful outcomes with surgical intervention, while other patients improved with medical management. Our patient responded well to medical management.

EBTB is a distinct form of TB that is associated with potentially serious complications. The young, the elderly and females are particularly vulnerable to the disease. Early diagnosis and initiation of ATT are essential to avoid complications such as tracheobronchial stenosis. While ATT is the key component of treatment, advanced bronchoscopic procedures or surgical intervention are required in some cases. Corticosteroids have been used as adjuvant therapy in the treatment of EBTB; however, their role is controversial.^[1]