Introduction

Amyloidosis comprises a heterogeneous group of disorders characterized by extracellular deposition of misfolded protein fibrils that exhibit Congo red positivity with apple-green birefringence under polarized light.[1,2] Based on distribution, amyloidosis is classified as systemic or localized. Localized tracheobronchial amyloidosis (TBA) is an uncommon entity, accounting for less than 1% of benign tracheobronchial tumors and a very small proportion of all amyloidosis cases.[1-3] It is most frequently associated with AL-type (light chain) amyloid produced locally by plasma cells.

Clinically, TBA often presents with nonspecific symptoms such as chronic cough, dyspnea, wheezing, recurrent respiratory infections, or hemoptysis, and may mimic asthma, chronic obstructive pulmonary disease, or tracheal stenosis.[3-5] Radiological findings are often subtle or nonspecific, making bronchoscopy with histopathological confirmation essential for diagnosis. Due to its rarity, there are no standardized management guidelines, and treatment is individualized based on symptom severity and extent of airway involvement. We report a case of TBA managed successfully with bronchoscopic intervention.

Case Report

A 55-year-old male presented to the respiratory medicine outpatient department with complaints of chronic cough, progressive exertional dyspnea for six months, and hoarseness of voice. The dyspnea had gradually worsened over time and was associated with intermittent wheezing. He also reported occasional episodes of scanty hemoptysis. There was no history of smoking, pulmonary tuberculosis, occupational exposure, connective tissue disease, or long-term medication use. In view of the hoarseness of voice, an otorhinolaryngology (ENT) evaluation was sought to assess for possible vocal cord pathology. No significant weight loss, fever, or dysphagia was reported.

Vital signs were stable. Respiratory system examination revealed bilateral expiratory wheeze without stridor. Cardiovascular, abdominal, and neurological examinations were unremarkable.

Routine laboratory investigations including complete blood count, renal function tests, and liver function tests were within normal limits. Inflammatory markers were mildly elevated. Serum and urine protein electrophoresis, along with serum free light chain assay, did not reveal monoclonal gammopathy. Autoimmune workup was negative.

Computed tomography (CT) of the chest demonstrated irregular circumferential thickening of the tracheal wall with multiple calcified nodular deposits causing significant luminal narrowing of the trachea and proximal main bronchi, a pattern described in tracheobronchialpappilomatosis.[4,6] There was no evidence of lung parenchymal mass, mediastinal lymphadenopathy, or pleural effusion.

Figure 1: CT chest showing tracheal wall	Figure 2: CT chest showing tracheal wall thickening and nodularities.

Flexible bronchoscopy was planned following ENT assessment. Indirect laryngoscopy revealed nodular lesions involving the vocal cords, raising suspicion of an infiltrative pathology. Initial flexible bronchoscopy demonstrated that the lesions originated at the level of the vocal cords, with extension into the trachea. Multiple pale-yellow, waxy nodular lesions were seen involving the anterior and lateral walls of the trachea, resulting in marked luminal narrowing, which is characteristic of tracheobronchial papilomatosis.[3,5] The mucosa appeared firm and brittle. Endobronchial biopsies obtained from the accessible lesions.

Figure 3: Flexible bronchoscopy revealed multiple nodular lesions seen arising from the trachea to both bronchial tree.

Histopathological examination showed subepithelial deposition of amorphous eosinophilic material, with Congo red positivity and apple-green birefringence under polarized light, confirming amyloidosis.[1,2] Congo red staining was positive, and apple-green birefringence was demonstrated under polarized light microscopy, confirming amyloid deposition. Immunohistochemical analysis was consistent with AL (lambda light chain) type amyloid. No evidence of malignancy, granulomatous inflammation, or vasculitis was noted.

Figure 4: Amorphous and homogenous	Figure 5: Congo red stain showing apple green eosinophils deposits, birefringence under polarized light

Further evaluation to exclude systemic amyloidosis included electrocardiography, echocardiography, serum B-type natriuretic peptide, renal evaluation, and abdominal imaging, all of which were within normal limits. Based on these findings, a diagnosis of extensive tracheobronchial amyloidosis was established.

Subsequently, the patient underwent mechanical debulking of the obstructing lesion followed by argon plasma coagulation (APC) to achieve airway patency and hemostasis. The procedure was well tolerated without complications. Post-procedure, the patient reported significant symptomatic improvement. In addition, the patient was initiated on oral colchicine at a dose of 1.5 mg/day as adjunctive medical therapy. Follow-up bronchoscopy at three months showed reduced lesion burden, and at six months the patient remained asymptomatic with no evidence of recurrence.

Discussion

Tracheobronchial amyloidosis is a rare localized form of amyloidosis characterized by amyloid deposition confined to the airway walls.[1,3] The majority of cases are of AL type, resulting from local plasma cell dyscrasia rather than systemic disease. The pathogenesis involves local production of immunoglobulin light chains, which misfold and deposit in the submucosa, leading to progressive airway narrowing.

The clinical presentation of TBA is often insidious and nonspecific, resulting in frequent misdiagnosis.[3-5] Wheezing and dyspnea may lead to an erroneous diagnosis of asthma or chronic obstructive pulmonary disease, while hemoptysis and recurrent infections may raise suspicion for malignancy or tuberculosis. Imaging findings such as tracheal wall thickening, nodularity, and calcification can suggest the diagnosis but are not diagnostic.

Bronchoscopy plays a pivotal role in both diagnosis and management of tracheobronchial amyloidosis.[3-8] The characteristic bronchoscopic appearance of pale-yellow, waxy nodules with a friable or brittle mucosa should raise suspicion of amyloidosis. Histopathological confirmation with Congo red staining remains the gold standard. Importantly, exclusion of systemic amyloidosis is mandatory, as management and prognosis differ significantly.

There is no definitive curative therapy for localized TBA, and management is primarily directed toward relieving airway obstruction and improving symptoms.[3,5,8] Bronchoscopic interventions such as mechanical debulking, laser therapy, argon plasma coagulation, cryotherapy, and stent placement have been used with varying success. Among these, argon plasma coagulation is widely favored due to its efficacy, precision, and favorable safety profile.[8,9] Radiotherapy has been reported in selected refractory cases. Systemic therapies used for systemic amyloidosis have limited or no role in localized disease.

The prognosis of TBA is generally favorable compared to systemic amyloidosis; however, recurrence is common, necessitating long-term follow-up with periodic bronchoscopic surveillance.[3-6] Early recognition and timely intervention can significantly improve quality of life and prevent life-threatening airway compromise.

In addition to bronchoscopic interventions, colchicine has been used as an adjunctive medical therapy in selected cases of localized amyloidosis, based on its anti-inflammatory properties and ability to inhibit amyloid fibril formation. Although evidence supporting its use in tracheobronchial amyloidosis is limited to case reports and small series, colchicine may help reduce local inflammation and slow progression when used alongside interventional therapies.[10,11]

Conclusion

Tracheobronchial amyloidosis is an uncommon but important cause of unexplained airway obstruction. Its nonspecific clinical presentation often leads to delayed diagnosis. A high index of suspicion, combined with radiological evaluation and confirmatory bronchoscopic biopsy, is essential for diagnosis. Bronchoscopic debulking with argon plasma coagulation is an effective treatment modality that provides symptomatic relief. Regular follow-up is essential due to the risk of recurrence.

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