Tracheobronchopathia osteochondroplastica as an unusual cause of chronic cough

Abstract

A cough that persists for more than 8 weeks is defined as a chronic cough. In routine practice, asthma, gastroesophageal reflux disease, and postnasal drip are the most common causes of chronic cough. A 58-year-old non-smoking male patient with no known comorbidities presented with a 3-month history of non-productive cough. Clinically, the respiratory system examination was normal, and radiological evaluation showed tracheal nodularity on computed tomography scan. He was then subjected to bronchoscopy, which showed multiple white-colored nodules involving the anterolateral wall of the tracheobronchial tree with the sparing of the posterior membranous wall. The bronchoscopic picture was the characteristic of Tracheobronchopathia osteochondroplastica (TBOP) and was later confirmed on histopathological examination of the nodules. TBOP presenting as chronic cough is very rare. It is a rare benign disease of the tracheobronchial tree and does not warrant any active intervention in the majority of patients.

Introduction

A cough that persists for more than 8 weeks is defined as a chronic cough. It is a commonly encountered symptom in general practice and studies have shown that roughly 11–18% of the population suffers from it.¹ In routine practice, asthma, gastroesophageal reflux disease, and postnasal drip are the most common causes of chronic cough. Tracheobronchopathia osteochondroplastica (TBOP) presenting as chronic cough is very rare. It is a benign disease of unknown etiology affecting the tracheobronchial tree. The presence of cartilaginous or osseous nodules in the submucosa of the tracheobronchial tree characterizes this disease.² These nodules protrude into the tracheobronchial lumen and, in few patients, can be severe enough to compromise the airway lumen. The disease was first described in 1857 by Wilks in a patient with pulmonary tuberculosis.³ The majority of patients have no symptoms, and the condition is usually diagnosed by chance during difficult endotracheal intubation or bronchoscopy.⁴ Herein, we report a case of TBOP presenting as chronic cough.

Case Report

A 58-year-old non-smoking male patient initially presented with a 3-month history of non-productive cough. He denied history of breathlessness, wheezing, allergic symptoms (recurrent cold, running nose), acid reflux, and constitutional symptoms associated with it. There was no history suggestive of postnasal drip. There was no diurnal or postural variation associated with the cough. Clinically, there were no significant abnormalities on the general physical examination and the respiratory system examination. An ear, nose, and throat examination was also normal. His blood investigations and chest radiograph were normal. His spirometry results [FVC- 2.94 (81%), FEV1-2.19 (70%), Forced expiratory volume in 1 second/Forced vital capacity (FEV1/FVC)- 74%] were also with in normal limits. He was started empirically on inhaled bronchodilators and steroids (budesonide 200 mcg plus formoterol 6 mcg once a day) along with antihistaminics and was advised to review after 4 weeks. He continued to be symptomatic at the time of review. He underwent computed tomography (CT) scan of the thorax (Fig. 1) which showed tracheal nodularity involving the anterolateral wall. He was then subjected to fiberoptic bronchoscopy which revealed multiple white-colored nodules involving the mucosal surface of the trachea and both main bronchi. The posterior membranous tracheal wall was spared with normal looking mucosa (Fig. 2, Fig. 3). During bronchoscopy, biopsies of the nodules were taken. Histopathological examination showed 3 tissue bits focally lined by pseudostratified ciliated columnar epithelium. The subepithelial layer showed extensive fibrosis and osseocartilaginous nodules. There was no evidence of epitheloid cell granulomas, necrosis, dysplasia, or malignancy (Fig. 4). The characteristic bronchocoscopic appearance along with histopathological findings favored the diagnosis of TBOP. He was counseled about his disease and was started on cough suppressants. An informed consent was also obtained from the patient for use of the clinical images in the study.

Fig. 1.

CT scan of the thorax showing tracheal nodularity involving anterolateral tracheal wall. CT, computed tomography.

Fig. 2.

FOB showed numerous greyish-white sessile nodules protruding into the trachea with sparing of posterior wall. FOB, fiberoptic bronchoscopy.

Fig. 3.

Involvement of right and left main bronchi.

Fig. 4.

Endobronchial biopsy showing pseudostratified columnar lining. Sub epithelium shows presence of osseocartilaginous nodules (40x).

Discussion

TBOP is a rare benign disease of the tracheobronchial tree. In this disease, there are multiple submucosal osseocartilaginous nodules in the trachea and larger bronchi. It has an incidence ranging from 0.01 to 4.2 per 100,000 individuals, with no gender predilection. The majority of patients are diagnosed in the 5th or 6th decade of life.⁵ It can be asymptomatic or associated with respiratory symptoms like chronic cough, dyspnea, and hemoptysis. A study by Zhu et al reported chronic cough to be the most common symptom in patients with TBOP.⁵ Our case too was symptomatic with chronic non-productive cough, which was refractory to inhaled bronchodilators, steroids, and antihistaminics. The severity of symptoms is often correlated with the location and extent of tracheobronchial involvement.

In the majority of cases, it is diagnosed accidentally at the time of difficult endotracheal intubation or during bronchoscopy.⁴ A chest radiograph is frequently non-diagnostic, and a CT scan of the thorax is the best non-invasive method for the diagnosis.⁵ Findings on CT scans are nodularity and irregular thickening of tracheobronchial cartilage with sparing of posterior tracheal wall. Some of these nodules may show calcification.⁶ However, there are case reports of TBOP in which there were no radiological abnormalities.⁷ In our case, CT scan thorax revealed tracheal nodularity and was confirmed on fiberoptic bronchoscopy which showed multiple white-colored nodules involving anterolateral wall of the tracheobronchial tree. The posterior tracheal wall was spared with normal looking mucosa. These findings were typical of TBOP.⁸ The characteristic sparing of the posterior wall of the trachea is a key feature of TBOP that differentiates it from diseases like endobronchial tuberculosis, tracheobronchial amyloidosis, sarcoidosis, and endobronchial neoplasms, which can also present with chronic cough.¹⁰ Histopathological examination of the nodules remains the most important step to confirm the diagnosis of this disease. Biopsies usually show multiple well-developed osseocartilaginous nodules in the submucosa, together with variable inflammatory infiltration.¹¹ The etiology of TBOP remains unclear and suspected causative factors include chronic infection (mycobacterial infection, helicobacter pylori), chemical or mechanical irritation, congenital abnormality, and metabolic disorders. One of the postulated theories on pathogenesis of TBOP is the transformation of undifferentiated cells in the internal elastic membrane of submucosa to osseocartilaginous tissue.¹² Bone morphogenetic protein-2 and transforming growth factor beta-1 have also been implicated in the formation of osseocartilaginous nodules in the tracheobronchial submucosa.^12,13

Currently, there is no consensus on the treatment of TBOP, and most therapies are palliative, focusing on the symptoms. Few patients of TBOP presenting with dyspnea and cough have shown symptomatic improvement with the administration of inhaled corticosteroids.⁴ However, our patient did not show any improvement in cough with inhaled corticosteroids and was later started on cough suppressants. Possible treatment strategies for severe disease associated with significant airway involvement and obstruction include bronchoscopy-guided excision or laser ablation, surgical resection, and even radiotherapy in few cases.^9,14,15 Most reports suggest the majority of patients have stable symptoms for many years and does not warrant any active intervention.¹¹ For this reason, and to avoid unnecessary treatment, it is important to be aware of this condition and its characteristics.

Conclusion

TBOP is an idiopathic disease of the tracheobronchial tree and can be a rare cause of persistent chronic cough. The typical appearance on bronchoscopy and histopathological findings of the nodular lesions play an important role in the diagnosis of TBOP. It is a benign disease and does not warrant any active intervention in the majority of patients.

Patients/ Guardians/ Participants consent

Patients informed consent was obtained.

Ethical clearance

Not Applicable.

Source of support

Nil.

Disclosure of competing interest

The authors have none to declare.