Tracheobronchial Amyloidosis: CT
A CT scan of the chest demonstrated a central lung mass at the level of the right mainstem bronchus. Flexible bronchoscopy revealed thickening of the distal trachea and obstruction of the right mainstem bronchus by a tumor-like exophytic mass. Pathology from endobronchial biopsies revealed bronchial mucosa with squamous metaplasia. Rigid bronchoscopy was performed and demonstrated the same finding of occlusion of the right main-stem bronchus but was complicated by significant bleeding during the procedure, requiring mechanical ventilation.
The patient was subsequently transferred to our institution. CT of the chest was repeated, revealing significant circumferential thickening with partial calcification of the right mainstem bronchus extending inferiorly to obliterate the right lower lobe bronchus (Fig 1). A 3 X 3-mm soft-tissue mass with an intraluminal component partially obstructing the right upper lobe bronchus was also identified. Source
Pulmonary function testing revealed FEV1 of 1.25 L (54% of predicted), FVC of 1.75 L (55% of predicted), FEV1/FVC ratio of 72%, total lung capacity of 3.12 L (59% of predicted), and diffusing capacity of 8.16 mL/min/mm Hg (37% of predicted). A repeat fiberoptic bronchoscopy revealed thickening of the mucosa over the distal trachea and carina and 75% occlusion of the right mainstem bronchus by an exophytic mass (Fig 2). The right upper lobe could not be visualized. The bronchus intermedius, right middle, and right lower lobe bronchi also had significant abnormal thickening of the mucosa causing significant narrowing. Biopsy specimen of the endobronchial mass demonstrated green birefringence with Congo red staining and was immunoreactive for к and X light chains. Serum protein electrophoresis, urine protein electrophoresis, and echocardiography failed to demonstrate evidence of systemic amyloidosis.
Figure 1. CT of the chest revealing significant circumferential thickening with partial calcification of the right mainstem bronchus extending inferiorly to obliterate the right lower lobe bronchus (arrow) with accompanying right pleural effusion (top) [arrowhead] and right lower lobe atelectasis (bottom) [arrow].
Figure 2. Initial bronchoscopy showed near-complete obliteration of the right mainstem bronchus by an exophytic mass.