Tracheobronchial amyloidosis is a rare disorder of unknown cause associated with the extracellular deposition of amyloid protein in a characteristic spatial structure of beta-sheet fibrils assembled into bundles. This protein stains with Congo red and shows apple-green birefringence under polarized light. The present case, which represents the nodular form of tracheobronchial amyloidosis, is the least common form of pulmonary amyloidosis with less than 20 cases reported.
An 81 year old female presented to the outpatient pulmonary clinic with shortness of breath and wheezing. She was recently hospitalized with a left lower lobe pneumonia. Her past medical history included “asthma,” pneumonia, hypertension, and acid reflux disease. She had no relevant surgical, social or family history. Her vital signs, physical examination, laboratory studies, spirometry and conventional chest x-rays were normal. Subsequent contrast enhanced chest computed tomography (CT) scan demonstrated multiple tracheal masses, left lower lobe posterior basilar collapse, and calcification of the cartilaginous tracheal rings and posterior membrane. Bronchoscopy demonstrated multiple fixed, firm, nodular hypervascular tracheal masses less than one centimeter in diameter, scattered hard irregular yellow plaques, and abnormal submucosal infiltration of the anterior main carina. There were no endobronchial abnormalities noted in the left lower lobe. [Figure 1] Forceps biopsy of the distal right tracheal lesion demonstrated eosinophilic paucicellular fibrosis with foci of calcification and congo red stain demonstrated submucosal amyloid deposits with apple-green birefringence under polarized light consistent with a diagnosis of nodular tracheobronchial amyloidosis. [Figures 2].
Patients with nodular tracheobronchial amyloidosis may present with shortness of breath, exertional dyspnea, hoarseness, cough, wheezing, and hemoptysis due to endobronchial obstruction or infiltration. Occasionally, patients present with recurrent post-obstructive pneumonia or endobronchial stenosis. Patients are often incorrectly diagnosed with asthma, pneumonia, or tracheobronchitis. Our patient presented with a history of recurrent pneumonias and was initially thought to have asthma. Spirometry may be helpful in detecting proximal nodular tracheal amyloidosis with classic inspiratory and expiratory loop truncation associated with fixed upper airway disease. In tracheobronchial amyloidosis, calcification typically involves both the cartilaginous rings and the membranous portion between the tracheal rings and/or the posterior membrane. This is a distinguishing feature on chest CT from tracheobronchopathia osteochondroplastica, in which calcification is reportedly confined to the anterior cartilaginous rings. Tracheobronchial amyloidosis typically show a bronchoscopic appearance of multiple bumps or endobronchial masses with overlying normal mucosa. Histologically, tracheobronchial amyloidosis can show osseous metaplasia and dystrophic calcification in addition to submucosal fibrosis. Congo red staining should be performed to evaluate for the possibility of tracheobronchial amyloidosis. Currently, the mainstay of treatment for tracheobronchial amyloidosis is debridement of symptomatic luminal obstruction via endoscopic resection and/or Nd-YAG laser therapy. Some patients may be amenable to endoscopic debridement with airway stenting or by-pass tracheostomy. External beam radiation therapy has been reportedly successful for some patients with symptomatic luminal obstruction. Open surgical resection or tracheoplasty is an option for those with diffuse disease. Once the diagnosis is established, early consultation with an interventional pulmonologist is strongly recommended. Our patient elected continued observation with a contingency plan to seek an interventional pulmonology consultation for evaluation of Nd:YAG laser therapy.
Patients with tracheobronchial amyloidosis may present with symptoms of dyspnea, localized wheezing, cough, hemoptysis, or recurrent pneumonias. Patients are often misdiagnosed with asthma, recurrent pneumonia or tracheobronchitis, and the true cause may not be recognized. Tracheobronchial amyloidosis can be confirmed by demonstrating the presence of submucosal amyloid deposition with Congo red staining. The mainstay of therapy is debridement of symptomatic luminal obstruction. Early referral to an interventional pulmonologist is recommended for possible endoscopic debridement and/or Nd-YAG laser therapy. Other treatment strategies include airway stenting, external beam radiation therapy, by-pass tracheostomy, or open surgical resection.
Krish Bhadra, No Financial Disclosure Information; No Product/Research Disclosure Information