Teaching Case

A 65-year-old female with severe persistent asthmatic bronchitis, seasonal allergy, gastroesophageal reflux disease (GERD) presented to her pulmonologist with shortness of breath for a year. She smoked 1 pack per day for 7 years and quit 41 years ago. A recent chest x-ray was negative for acute cardiopulmonary findings. A non-contrast CT was ordered for further evaluation.

Non-contrast CT images showed scalloping of the tracheal wall with multiple small nodular, non-calcified lesions in the trachea and the proximal left main bronchus sparing the posterior membranous portion of the trachea (Figure 1-4).

Tracheobronchopathia osteochondroplastica (TO) is one of the diffuse non-neoplastic diseases of the central airway.  TO affects the anterior tracheal wall and the major bronchi, characterised by multiple submucosal osteocartilaginous nodules. The most commonly affected locations are the lower trachea and the proximal portions of the primary bronchi [1]. The nodules consist of hyaline cartilage with sparing of the posterior membranous tracheal wall, in contrast to tracheobronchial amyloidosis, tracheobronchial papillomatosis, and granulomatosis with polyangiitis (GPA) in which the posterior wall is affected [2]. TO is frequently found in patients in their mid-50s, and affects more men than women with a ratio of 3:1 [1]. A study in which 2180 people underwent bronchoscopy showed 9 patients had TO, making the prevalence among this population 0.37%. These findings were consistent with other researchers which showed it to be 0.02- 0.7% [1]. 

The aetiology of TO is unknown. One proposed mechanism by Tajima et al was the involvement of bone morphogenic protein-2(BMP-2) and transforming growth factor-beta 1 (TGF-1) in causing formation of cartilaginous nodules [3]. It does not have relation with smoking or other systemic disorders [4].

Although most patients are asymptomatic, the symptomatic patients can present with nonspecific respiratory symptoms such as cough, dyspnea on exertion, recurrent infection, wheezing and sometimes hemoptysis. Hemoptysis occurs secondary to mucosal breakage from the rubbing between the opposing nodules [1]. In even more rare occasions, airway obstruction can be found in one or more parts of the trachea and bronchi in patients with severe disease [2]. TO is frequently misdiagnosed as asthma since the presentations can be very similar [4]. In 8/9 of the patients diagnosed with TO, spirometry showed an obstructive lung pattern, further showing how TO can be misdiagnosed as asthma [5]. 

Radiological appearance of TO ranges from tracheal scalloping, nodular irregularity to varying degree of asymmetric stenosis. On CT, irregular calcifications in the thickened tracheal cartilage can be seen (Figure 1-4). The posterior membrane of the trachea is spared from the nodules [1]. During bronchoscopy, multiple smooth, raised, white, osteocartilaginous nodules can be found (Figure 5). The hard density of those nodules makes biopsy difficult, although biopsy has shown osteocartilaginous tissue [6]. 

Most patients with TO are asymptomatic and treatment is not necessary. Currently, there is no specific treatment to remove the existing nodules or to prevent the development of new nodules [1]. One study showed tracheoplasty successfully alleviated symptoms of a few patients with severe and symptomatic disease with follow up to 12 years [2]. The mainstay for management of TO is bronchodilators. Although treatment of pulmonary infections and bronchoscopic dilation can also be used if clinically indicated [4].

Written informed patient consent for publication has been obtained.