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A 62-year-old, non-smoking male is admitted to the hospital with hoarseness and a non-productive cough. He reports that these symptoms began about 2 months previously. His physician prescribed salmeterol/fluticasone (25/250 μg twice daily) to manage his cough.

However, 2 weeks prior to his admission to the hospital, his coughing increased in frequency despite his use of the inhaler. He reports that he has no prior history of respiratory disease, and no known allergies.

Findings on chest radiography (RX) and computed tomography (CT) are unremarkable. Because this patient's symptoms have persisted for months, and to rule out a neoplastic etiology, clinicians perform fiberoptic bronchoscopy with biopsies. Examination reveals partly conglomerated sessile nodules protruding into the tracheobronchial lumen, which produce a gritty sensation as the scope moves through the narrowed lumen.

Importantly, the mucosa of the posterior membranous tracheal wall is not affected and appears normal. However, the airway wall is rigid and presents with hard nodules that impede the scope's forward movement.

Histopathology findings

Histopathology examination of the biopsy samples -- six minimal grayish fragments measuring 0.3-0.6 cm -- identifies cartilaginous and osseous submucosal nodules consistent with the diagnosis of TO.

Histopathological examination reveals disseminated erosions of the respiratory epithelium with extensive foci of squamous metaplasia.

The submucosa contains numerous well-developed cartilaginous and osseous nodules, interspersed with inflammatory cells, primarily lymphocytes and histiocytes.

Appearance of the calcified nodules is varied, and includes:

• Unusual elongated morphology (potentially connected with the perichondrium of the tracheal rings)
• Nodules more similar to a central island of osteocytes, not connected with nearby structures

Diagnosis

Based on the histological features, as well as clinical and endoscopic findings, clinicians diagnose this patient with tracheobronchopathia osteochondroplastica (TO).¹

Discussion

Tracheobronchopathia osteochondroplastica is a rare, benign, and often asymptomatic disease of undetermined etiology. Detection rates are very low – in fact, the disease is often an incidental finding during intubation or endoscopy.

Only about 400 cases have been reported to date, and no diagnostic or treatment guidelines have been developed.² A of the literature suggests TO is very rarely diagnosed in people younger than age 50.³

Because TO generally progresses very slowly and has non-specific symptoms⁴– e.g., chronic breathlessness on exertion, chest pain, or less commonly, hemoptysis and constitutional symptoms – it is often mistaken for allergies or asthma.⁵ For this reason, and to avoid unnecessary treatments, authors reporting this case aim to increase awareness of TO.

Accurate diagnosis requires extensive clinical, radiologic, and endoscopic investigations, usually but not necessarily including histopathological examination of biopsies.⁶

Upon clinical examination, chest auscultation may detect wheezing, stridor, and crackles.³

Computerized tomography (CT) scan offers a non-invasive approach to initial of tracheobronchial lesions. Findings on CT scans usually include mucosal abnormalities and calcified nodular densities protruding into the tracheal lumen, with an abnormally irregular tracheal morphology and decreased lateral diameter.⁶ However, findings may be unremarkable in some patients, as in this reported case.

Bronchoscopic examination that detects nodular lesions of the large airway should prompt consideration of TO. Bronchoscopy typically reveals nodules in the submucosa of anterolateral walls of the trachea and bronchus, but not on the posterior wall of the trachea (due to the lack of cartilage). This sparing on the posterior wall is a key to differentiating TO from other diseases with nodular appearance, such as amyloidosis, papillomatosis, polychondritis, and sarcoidosis.⁷

Histopathological findings vary but typically include squamous metaplasia – which has been suggested may represent the initial stage of development – followed by or concurrent with cartilage formation, ossification, and/or calcification in the submucosa.⁴

While conventional bronchoscopy is considered the gold standard for diagnosing TO, more recently developed endoscopic techniques may increase detection of subtle mucosal changes associated with TO.

(AFI) is one such recent advancement in bronchoscopy that is widely used by clinical oncologists to aid in early detection of malignant lesions. In TO, it detects weak autofluorescence signals from the bronchial mucosa, and uses different colours to distinguish abnormal from normal bronchial mucosa.

AFI has been suggested as having a potential role in detection of tracheal involvement in TO, although further study is needed to clarify its clinical utility in this context.⁸

Treatment

Authors of note that in the absence of a standard approach to treatment, the approach is generally palliative and focuses on managing symptoms. Treatment with inhaled beclomethasone dipropionate and budesonide has been shown effective in resolving acute dyspnea in patients with TO.

In patients with severe TO complicated by significant airway stenosis or recurrent obstructive infection, laser ablation and surgical resection are reasonable options. Lesions that are creating significant airway obstruction may be endoscopically removed.

Conclusion

Case report authors caution that diagnosis of this rare idiopathic disease is rarely simple or rapid, and typically requires a multidisciplinary approach.

References

1. Riva G et al. Tracheobronchopathia osteochondroplastica: Diagnosis of an uncommon disease. Am J Case Rep 2019;20:74-77

2. Zhu Y et al. A clinical study of tracheobronchopathia osteochondroplastica: Findings from a large Chinese cohort. PLoS One 2014;9

3. Jabbardarjani HR et al. Tracheobronchopathia osteochondroplastica: Presentation of ten cases and review of the literature. Lung 2008;186:293–97

4. Leske V et al. Tracheobronchopathia osteochondroplastica: A study of 41 patients. Medicine (Baltimore) 2001;80:378–90

5. Fois AG et al: Tracheobronchopathia osteochondroplastica: A rare case report of a non-smoker and non-atopic patient, with a long history of wheezing since childhood. Multidiscip Respir Med 2016;11:16

6. Devaraja K et al. Tracheobronchopathia osteochondroplastica: Awareness is the key for diagnosis and management. BMJ Case Rep 2017.

7. Nielsen SW et al. Dyspnea, dysphonia, and cough: Varied presentations of tracheobronchopathia osteochondroplastica. Ann Otol Rhinol Laryngol 2015;124:829–33

8. Ihara H et al: Autofluorescence imaging bronchoscopy as a novel approach to the management of tracheobronchopathia osteochondroplastica: A case report. J Thorac Dis 2016;8: E1195–98

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