Tracheobronchial amyloidosis

A 38-year old male patient with prior history of pulmonary embolism and factor V Leiden thrombophilia visited our emergency department, because of respiratory dependent chest pain. The patient complained about sputum production and haemoptysis for at least one week. Laboratory tests showed a D-dimer of 920 µg/L.

Because of high suspicion of pulmonary embolism CT angiography was performed which revealed no contrast filling defects, thrombi or other signs of pulmonary embolism. However, there was a continuous irregular circumferential mucosal wall thickening of the distal trachea, the entire left main bronchus and the proximal left segmental bronchi, with significant narrowing of the left bronchial lumen (Fig. 1). Within the mucosal thickening some small calcifications were identified (Fig. 2). Some deposits were present in a few left lower lobe (sub)segmental bronchi. Small consolidations were seen in the right lower lobe and in the lingula. The patient was referred to a pulmonologist and a bronchoscopy-guided biopsy was performed. The biopsy specimens contained both normal and metaplastic squamous cell epithelium. Deposition of homogenous eosinophilic amorphic material was seen in the underlying stroma. Congo red stain was positive, confirming the patient suffering from primary tracheobronchial amyloidosis (TBA).

Pulmonary amyloidosis is a rare disease, which is characterised by extracellular deposition of fibrillary proteins in the lungs. In amyloidosis, respiratory involvement occurs in 50 % of patients [1]. Fraser et al. were the first to develop a radiological classification system for pulmonary amyloidosis in which they described tracheobronchial, nodular parenchymal and diffuse interstitial forms of amyloidosis [2]. Lymphatic, laryngeal, and pleural impairment have also been described [3, 4]. Patients with tracheobronchial amyloidosis may not always present with symptoms, depending on the extent of mucosal wall thickening. Symptoms commonly seen in patients with TBA are cough, wheezing, dyspnoea, haemoptysis, stridor and recurrent pneumonia [5, 6]. In radiological examination, tracheal and bronchial submucosal wall thickening with irregular calcifications and luminal narrowing can be seen on thoracic CT imaging. The differential diagnosis includes diffuse tracheal diseases such as tracheobronchopathia osteochondroplastica (TBO), relapsing polychondritis, Wegener granulomatosis, sarcoidosis, inflammatory bowel tracheobronchitis, tracheobronchial paracoccidioidomycosis, tuberculosis, as well as malignancy such as lymphoma and bronchial carcinoma [1]. High resolution CT is able to discriminate between some of these entities. In TBA small calcifications involving tracheal or bronchial segments are sometimes present, but these are not specific for diagnosis. In patients with tracheal mucosal wall thickening, the tracheal posterior membrane should classically be involved. The distribution of mucosal wall thickening can either be focal or diffuse. Primary tracheobronchial amyloidosis should be considered when no other abnormalities can be identified. Tissue biopsy is essential for a definitive diagnosis. Amyloidosis is a benign lesion, but can be fatal due to airway obstruction or respiratory failure [6]. Resection of obstructive masses using laser techniques and bronchoscopic dilatation or stent implantation are treatment options for TBA. Since the airway lesions in our patient also extended throughout the segmental bronchi, endobronchial treatment was not expected to be sufficient. Radiotherapy is an alternative treatment for patients with extensive disease. Recently, new forms of treatment like colchicine have suggested by some authors [7].