CONTENTS

• Guide to the differential diagnosis: 
  • Bronchoscopic findings
  • CT scan findings
  • Flow-volume loops ➡️
• Specific disorders
  • Bilateral vocal fold paralysis
  • Stenosis
    • Laryngeal stenosis
    • Tracheal stenosis
  • Tracheobronchomalacia (TBM)
  • Congenital tracheobronchomegaly (Mounier-Kuhn syndrome)
  • Tracheobronchopathia osteochondroplastica (TPO)
  • Tracheobronchial amyloidosis ➡️
  • Infectious:
    • Respiratory papillomatosis
    • Tracheobronchial aspergillosis ➡️
    • Broncholithiasis due to granulomatous mediastinitis ➡️
  • Inflammatory disorders:
    • Sarcoidosis ➡️
    • GPA (granulomatosis with polyangiitis) ➡️
    • Relapsing polychondritis
  • Fibrosing mediastinitis ➡️
  • Foreign body ➡️
  • Tracheoesophageal fistula (TEF)
  • Necrotic/pseudomembranous tissue:
    • Necrotizing tracheobronchitis
    • Obstructive fibrinous tracheal pseudomembrane
  • Sabre-sheath trachea
• Questions & discussion

abbreviations used in the pulmonary section: 4

• ABPA: Allergic bronchopulmonary aspergillosis 📖
• AE-ILD: Acute exacerbation of ILD 📖
• AEP: Acute eosinophilic pneumonia 📖
• AFB: Acid Fast Bacilli
• AIP: Acute interstitial pneumonia (Hamman-Rich syndrome) 📖
• ANA: Antinuclear antibody 📖
• ANCA: Antineutrophil cytoplasmic antibodies 📖
• ARDS: Acute respiratory distress syndrome 📖
• ASS: Antisynthetase Syndrome 📖
• BAL: Bronchoalveolar lavage 📖
• BiPAP: Bilevel positive airway pressure 📖
• CEP: Chronic eosinophilic pneumonia 📖
• CF: Cystic fibrosis 📖
• COP: Cryptogenic organizing pneumonia 📖
• CPAP: Continuous positive airway pressure 📖
• CPFE: Combined pulmonary fibrosis and emphysema 📖
• CTD-ILD: Connective tissue disease associated interstitial lung disease 📖
• CTEPH: Chronic thromboembolic pulmonary hypertension 📖
• DAD: Diffuse alveolar damage 📖
• DAH: Diffuse alveolar hemorrhage 📖
• DIP: Desquamative interstitial pneumonia 📖
• DLCO: Diffusing capacity for carbon monoxide 📖
• DRESS: Drug reaction with eosinophilia and systemic symptoms 📖
• EGPA: Eosinophilic granulomatosis with polyangiitis 📖
• FEV1: Forced expiratory volume in 1 second 📖
• FVC: Forced vital capacity 📖
• GGO: Ground glass opacity 📖
• GLILD: Granulomatous and lymphocytic interstitial lung disease 📖
• HFNC: High flow nasal cannula 📖
• HP: Hypersensitivity pneumonitis 📖
• IPAF: Interstitial pneumonia with autoimmune features 📖
• IPF: Idiopathic pulmonary fibrosis 📖
• IVIG: Intravenous immunoglobulin 📖
• LAM: Lymphangioleiomyomatosis 📖
• LIP: Lymphocytic interstitial pneumonia 📖
• MAC: Mycobacterium Avium complex 📖
• MCTD: Mixed connective tissue disease 📖
• NIV: Noninvasive ventilation (including CPAP or BiPAP) 📖
• NSIP: Nonspecific interstitial pneumonia 📖
• NTM: Non-tuberculous mycobacteria 📖
• OHS: Obesity hypoventilation syndrome 📖
• OP: Organizing pneumonia 📖
• OSA: Obstructive sleep apnea 📖
• PAP: Pulmonary alveolar proteinosis 📖
• PE: Pulmonary embolism 📖
• PFT: Pulmonary function test 📖
• PLCH: Pulmonary Langerhans Cell Histiocytosis 📖
• PPFE: Pleuroparenchymal fibroelastosis 📖
• PPF: Progressive pulmonary fibrosis 📖
• PVOD/PCH Pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis 📖
• RB-ILD: Respiratory bronchiolitis-associated interstitial lung disease 📖
• RP-ILD: Rapidly progressive interstitial lung disease 📖
• TNF: tumor necrosis factor
• UIP: Usual Interstitial Pneumonia 📖

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bronchoscopic findings in large airway disease

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causes of endobronchial mucosal nodules

• TPO (tracheobronchopathia osteochondroplastica).
• Amyloidosis.
• Sarcoidosis, Crohn disease.
• GPA (granulomatosis with polyangiitis).
• Infection:
  • Papillomatosis.
  • Rhinoscleroma.
  • Tuberculosis.
  • Fungal disease.
• Metastatic pulmonary calcification. (32386651)

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CT scan findings in large airway disease

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circumferential thickening suggests:

• Infectious tracheitis (e.g., tuberculosis).
• GPA (granulomatosis with polyangiitis).
• Amyloidosis.
• Rhinoscleroma.

sparing of the posterior wall suggests:

• Relapsing polychondritis.
• TPO (tracheobronchopathia osteochondroplastica).

calcification suggests:

• Amyloidosis.
• TPO (tracheobronchopathia osteochondroplastica).

ulceration:

• See the section on necrotizing tracheobronchitis and its related differential diagnosis: 📖

long-segment tracheal narrowing suggests:

• Amyloidosis.
• GPA (granulomatosis with polyangiitis).
• Tracheobronchomalacia.
• Relapsing polychondritis.
• Papillomatosis (if severe).
• Tracheobronchopathia osteochondroplastica.
• Sarcoidosis, inflammatory bowel disease.

diffuse airway wall thickening

• Asthma.
• Chronic bronchitis due to smoking.
• Relapsing polychondritis.
• Granulomatosis with polyangiitis.
• Sarcoidosis.
• IgG4-related disease.
• Airway involvement in inflammatory bowel disease.
• Amyloid or neoplastic cell infiltration. (34851243)

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bilateral vocal fold paralysis

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epidemiology

• Neck surgery (e.g., thyroidectomy) is the most common cause.
• Intubation may rarely cause this (especially if prolonged, larger size endotracheal tube and/or cuff were close to the vocal cords). This generally resolves within 10 weeks. (Fishman 2023)
• Various neurologic disorders, including: (Fishman 2023)
  • Parkinson disease.
  • Multiple sclerosis.
  • Amyotrophic lateral sclerosis.
  • Guillain-Barre syndrome.
  • Brainstem stroke.
  • Large cerebral hemisphere stroke.
  • Familial bulbar spinal muscle atrophy.
• Idiopathic paralysis may occur.

symptoms

• Acute paralysis may not cause dyspnea, since the vocal cords are left in a neutral position. Over ~3-6 months, partial reinnervation may cause the vocal cords to move into a medial position that leads to greater airway obstruction and causes dyspnea. (Murray 2022)
• Mild to moderate inspiratory stridor is often present.

pulmonary function tests

• Vocal cord paralysis causes variable extrathoracic obstruction, so this causes selective flattening of the inspiratory limb of the flow-volume curve.
• If maximal inspiratory flow is <1.5 L/min, patients are usually markedly symptomatic. (Murray 2022)

management

• Various surgical techniques may be utilized to lateralize the vocal cords, in efforts to improve airflow. Unfortunately, some of these may compromise the voice strength, causing a breathy voice.

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laryngeal stenosis

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basics

• Scarring usually involves the posterior portion (posterior glottic stenosis).

epidemiology

• This is usually caused by endotracheal intubation. Risk factors include:
  • Prolonged intubation.
  • Multiple intubations.
  • Intubation with a large endotracheal tube.
• Stenosis often develops within ~6 weeks following intubation.

laryngoscopy

• Findings may include immobile vocal cords, which may mimic bilateral vocal cord paralysis.
• Careful examination usually shows scar tissue near the cricoarytenoid joint. (Murray 2022)

pulmonary function tests

• This usually causes a fixed obstruction, causing flattening of both inspiratory and expiratory limbs of the flow-volume loop.

treatment

• Surgery can generally treat this successfully (e.g., with removal of the fibrotic tissue).

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tracheal stenosis

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epidemiology

• Postintubation:
  • Stenosis usually presents 2-12 weeks later, but can appear 1-2 years later.
  • Risk factors: (Murray 2022; Rosado-de-Christenson 2022)
    • Female sex
    • Obesity, diabetes, hypertension, cardiovascular disease.
    • Longer duration of intubation.
• Prior tracheostomy:
  • Risk factors: (Murray 2022)
    • Tracheostomy placement through the first tracheal ring (where the airway is narrow). This is more likely with percutaneous tracheostomy, so percutaneous technique is a risk factor.
    • Tube size >6.
    • Obesity.
• Idiopathic subglottic stenosis:
  • Almost exclusively seen in women.
  • Usually occurs ~50 years old.
  • May be associated with gastroesophageal reflux disease. (ERS handbook 3rd ed.)
• Infection:
  • Tuberculosis.
  • Fungal infection.
  • Klebsiella rhinoscleroma.
  • Corynebacterium pseudodiptheriticum.
• Inflammation:
  • GPA (granulomatosis with polyangiitis).
  • Relapsing polychondritis.
  • Sarcoidosis.
  • Inflammatory bowel disease.
  • IgG4-related disease.

clinical manifestations

• Dyspnea (often misdiagnosed as asthma or COPD).
• Stridor that may be both inspiratory and expiratory (due to a fixed obstruction).
• Ineffective secretion clearance, leading to recurrent pulmonary infection.
• Cough.
• Eventually, may lead to respiratory failure.

pulmonary function tests

• In symptomatic patients, a plateau of the flow-volume curve should be seen.

chest radiograph

• Stenosis is usually visible, but is often overlooked.

CT scan

• General:
  • CT scan may localize and characterize the stenotic area.
  • Stenosis may be diffuse or segmental.
  • Sensitivity may not be perfect, as a short area of obstruction may be missed.
    • Multiplanar reformats and virtual bronchoscopy improve performance.
    • Inspiratory and expiratory scans help differentiate fixed obstruction from tracheomalacia, or the combination of both. (Rosado-de-Christenson 2022)
• Postintubation tracheal stenosis:
  • Usually 3-4 cm below the cricoid cartilage.
  • Stenosis is focal, usually ~2 cm in craniocaudal length. (Walker 2019)
  • Stenosis typically has a smooth, hourglass configuration. (Shepard 2019)
  • Less frequently, stenosis may cause a thin membrane of granulation tissue to project into the lumen. This may be difficult to detect on axial CT images. (Walker 2019)
• Idiopathic laryngotracheal stenosis:
  • Mucosal and submucosal hypertrophy occurs that spares cartilage. (Murray 2022)
  • Usually stenosis is ~2-4 cm long.
  • Typically occurs in the subglottic area.
  • Variable appearance (smooth/tapered or irregular). (Shepard 2019)
• Radiological differential diagnosis:
  • Extrinsic compression of the airway.
  • Dynamic collapse of the trachea (tracheomalacia).
  • Tracheobronchopathia osteochondroplastica.
  • Tracheobronchial amyloidosis.

bronchoscopy

• May confirm the presence of tracheal stenosis, if this is in doubt.

management

• Avoid procedures that may increase edema of the tracheal mucosa.
• Patients who are asymptomatic may often be monitored serially, without immediate intervention.
• Simple stenosis (concentric, <1 cm length, without malacia): (Murray 2022)
  • Initial intervention may be endobronchial therapy including radial incision and dilation.
  • If recurrent stenosis occurs, then surgical resection may be preferred. Alternatively, if the patient isn't a surgical candidate, then repeat dilation +/- silicone stent may be utilized.
• Complex stenosis (many shapes, >1 cm in length, with malacia): (Murray 2022)
  • If surgically operable, then resection may be preferred (e.g., 1-4 cm in length, not high subglottic, and operative candidate).
  • If not surgically operable, then dilation plus silicone stenting may be necessary (e.g., >4-6 cm length, high subglottic, and/or inoperable candidate).

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tracheobronchomalacia

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basics

• Tracheobronchomalacia (TBM) is caused by weakness of the anteriolateral cartilaginous tracheal/bronchial walls, which causes expiratory flattening and collapse. This may involve all, or part of, the trachea.
  • Bronchomalacia refers to the same process, only involving the bronchi. (30131839)
• Excessive dynamic airway collapse (EDAC) is similar to tracheobronchomalacia. This refers to exaggerated bulging of the posterior tracheal membrane into the airway lumen during expiration. EDAC is found mostly in patients with chronic obstructive airway diseases or asthma, possibly due to exposure of the posterior trachea to wide swings in intrapleural pressure. (Murray 2022) Treatment may be similar to the treatment of tracheomalacia (discussed further below). 

epidemiology & causes

The incidence of tracheobronchomalacia is relatively high (e.g., it may be seen on ~1% of all bronchoscopies). Causes include:

• Chronic inflammation:
  • COPD (may occur in ~20% of patients with COPD).
  • Cystic fibrosis (up to 70% of adults). (Rosado-de-Christenson 2022)
  • Asthma.
  • Smoking and/or vaping.
  • One study found tracheobronchomalacia in 18% of patients with severe asthma. (34295405)
• Chronic external compression:
  • Thyroid mass.
  • Vascular ring or aneurysm.
  • Cardiomegaly.
  • Skeletal abnormality.
• Prior intubation.
• Surgery/trauma:
  • Trauma.
  • Status post lung transplantation or pneumonectomy.
• Rare causes:
  • Radiation therapy.
  • Tracheoesophageal fistula.
  • Mounier-Kuhn syndrome.
  • Relapsing polychondritis.
  • Idiopathic.

clinical manifestations

• Can be an incidental finding in patients who lack symptoms.
• Dyspnea and wheezing may occur.
• Cough and difficulty clearing secretions may predispose to recurrent infection. Eventually, this may lead to bronchiectasis.
• Cough may have a barking quality likened to a seal (caused by impingement of the anterior and posterior tracheal walls).
• ⚠️ Patients may deteriorate suddenly with induction of anesthesia – this is discussed further in the treatment section below. (Rosado-de-Christenson 2022) 

chest radiograph

• This will not reveal tracheobronchomalacia.

CT scan

• Tracheobronchomalacia is defined as >70% decrease in cross-sectional area with expiration. (26848604) This requires a combination of both inspiratory and expiratory CT scans. On expiratory scans, a frown-like configuration of the trachea may be seen (figure below).
  • In many healthy people, the trachea collapses posteriorly by ~50% on forced exhalation, so this finding alone may be nonspecific.
  • In order to require treatment, collapse usually approaches 95-100% during forced exhalation. (Murray 2022) 
  • ⚠️ Standard CT scans are obtained upon end-inspiration, so tracheobronchomalacia will generally be missed.
• Lunate trachea (aka crescentic tracheomalacia) may rarely be seen on inspiratory CT scans:
  • This is defined as a trachea whose coronal diameter is greater than its sagittal diameter at end-inspiration (see bottom left panel of the figure below).
  • Lunate trachea is poorly sensitive for tracheobronchomalacia, but specific.
• Tracheobronchomalacia may be focal or diffuse.

pulmonary function tests 

• Flow-volume loops may show four abnormalities: (figure below)
  • (1) Reduction in the peak expiratory flow (most common pattern).
  • (2) Biphasic morphology.
  • (3) Notched morphology – if seen, this may be especially suggestive of tracheobronchomalacia. (34295405)
  • (4) Oscillations.
• Performance:
  • Flow volume loops can be normal in patients with substantial tracheal collapse on CT scan and/or bronchoscopy. However, such patients probably don't have physiologically significant airway obstruction.
  • Overall, pulmonary function tests may have the greatest specificity to diagnose which patients have clinically relevant obstruction. (Murray 2022)

bronchoscopy

• Diagnosis is based on dynamic collapse of the trachea during expiration, by >50% in the anterior-posterior dimension.
• Different forms of tracheobronchomalacia may be noted:
  • Crescent-type tracheobronchomalacia (figure b below) – most common type of tracheobronchomalacia.
  • Sabre sheath-type tracheobronchomalacia (figure c below) – may be seen in COPD.
  • Circumferential tracheobronchomalacia (figure d below) – may be seen in relapsing polychondritis.

management

• Stabilization in the peri-anesthetic context:
  • Tracheobronchomegaly may cause deterioration with induction of anesthesia, since paralytics may facilitate tracheal collapse.
  • Acute management centers around the use of sufficient positive pressure to stent open the trachea (e.g., augmented levels of PEEP, extubation to BiPAP).
• Usual therapy:
  • Treat any underlying condition.
  • Nocturnal positive airway pressure may pneumatically stent the airway open, thereby relieving nocturnal symptoms. (Murray 2022)
  • An expiratory flutter valve (e.g., Acapella) may be useful to maintain airway patency while expiring, to promote airway clearance.
  • Bronchodilators may worsen tracheomalacia, due to relaxation of tracheal muscle tone. (26848604)
• Refractory symptoms may warrant additional therapy:
  • Silicone airway stenting is an option.
  • Tracheobronchoplasty involves surgical insertion of a mesh to reinforce the posterior tracheal wall. Temporary placement of a silicone airway stent may help determine which patients will potentially benefit from this procedure. (Murray 2022)

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congenital tracheobronchomegaly (Mounier-Kuhn syndrome)

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basics

• Mounier-Kuhn syndrome involves a congenital, idiopathic enlargement of the trachea and main bronchi.
• Atrophy or absence of elastic fibers causes the trachea to be dilated, flaccid, and collapsible upon expiration. This leads to ineffective secretion clearance, with subsequent infections.

epidemiology

• Mostly encountered in men in their ~20s-50s.
• The male:female ratio is ~10:1.
• Most cases are sporadic (although a familial form has been reported).

symptoms

• Clinical manifestations will tend to mimic bronchiectasis or chronic bronchitis:
  • Dyspnea.
  • Cough (which may be productive).
  • Hemoptysis.
  • Digital clubbing.
• Patients are predisposed to various pathologies:
  • Recurrent pulmonary infections.
  • Bronchiectasis.
  • Emphysema.
  • Pulmonary fibrosis.
  • Spontaneous pneumothorax.

radiology

• Two key findings are:
  • (1) Dramatic dilation of the trachea and main bronchi, with abrupt transition to normal-sized peripheral airways at the segmental level. (Shepard 2019) Unlike most other causes of bronchiectasis, bronchial walls are often thin. (Walker 2019)
  • (2) Tracheal diverticula may result from prolapse of weakened mucosa through the tracheal rings. This can produce a “corrugated” or “scalloped” appearance on CT scan (especially appreciated on sagittal images). If seen, this is specific for Mounier-Kuhn syndrome (as opposed to secondary tracheomegaly).
• Complications may also be seen:
  • Tracheobronchomalacia is common (dynamic collapse of trachea and central airways on expiratory imaging). (Shepard 2019)
  • Bronchiectasis may eventually develop.
  • Emphysema with bullous disease.
  • Perihilar pulmonary fibrosis.
  • Pneumothorax.
• Different types of Mounier-Kuhn syndrome: (Rosado-de-Christenson 2022)
  • Type 1: Symmetric diffuse dilation of the trachea and mainstem bronchi.
  • Type 2: Tracheal dilation and diverticula.
  • Type 3: Diverticula involve the trachea and distal bronchi.

differential diagnosis: acquired tracheomegaly

• Tracheobronchomegaly may result from systemic disorders:
  • Ehlers-Danlos syndrome.
  • Marfan syndrome.
  • Cutis laxa.
  • Ankylosing spondylitis.
• Tracheomegaly may occur in about a third of patients with diffuse pulmonary fibrosis, especially pulmonary fibrosis involving the upper lung zones (e.g., pleuroparenchymal fibroelastosis). This could relate to chronic cough and recurrent respiratory infections. (Walker 2019)

treatment

• Acute management may involve the use of positive airway pressure to provide a pneumatic stent which keeps airways open.
• (1) Airway clearance therapies to promote sputum clearance are important. Patients with established bronchiectasis may require further therapy for this, as discussed here: 📖
  • Antibiotics may be indicated during exacerbations.
• (2) Treatment of tracheobronchomalacia (if present) may rarely involve tracheal stenting. This is discussed further here: 📖

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tracheobronchopathia osteochondroplastica

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basics

• This is a rare disease with submucosal osseous and/or cartilaginous nodules within the anterolateral walls of the trachea (and to a lesser degree the proximal bronchi).
• Most often it is an incidental finding.

epidemiology

• Overall this is extremely rare.
• 3:1 male predominance.
• Patients are usually >50 years old.
• May be associated with tracheobronchial amyloidosis or atrophic rhinitis. (ERS handbook 3rd ed.)

symptoms

• The vast majority of patients are asymptomatic.
• Symptoms may include:
  • Chronic cough is the most common symptom. This may be accompanied by sputum production and occasionally hemoptysis.
  • Dyspnea, wheezing.
  • Recurrent pneumonia (if there is significant endobronchial obstruction). (33280770)

radiograph

• Typically normal.
• Potential findings:
  • Tracheal stenosis which is often asymmetric.
  • Tracheal calcification.
  • Tracheal wall nodularity.
  • If bronchi are obstructed, this may lead to lobar atelectasis and/or postobstructive pneumonia.

CT scan

• Only the anterolateral tracheal walls are affected (the posterior membrane is spared because it lacks cartilage).
• Tends to involve the lower two thirds of the trachea. Proximal bronchial walls may also be involved.
• Nodules (~1-5 mm) may protrude into the lumen, often with calcification.
• Stenosis may be present.
• Expiratory CT scan usually doesn't demonstrate dynamic tracheal collapse (unlike relapsing polychondritis). (Walker 2019)
• CT scan may miss milder forms of tracheobronchopathia osteochondroplastica. (33280770)

bronchoscopy

• Nodules may be seen protruding from the tracheal walls, with sparing of the posterior membrane (figure below).
• This is often described as a “rock garden” or “paving stone” appearance.

diagnosis

• Disorders that spare the posterior wall of the trachea include tracheobronchopathia osteochondroplastica and relapsing polychondritis, which are often not difficult to differentiate. Consequently, typical imaging features on CT scan may be sufficient for diagnosis (rendering bronchoscopy unnecessary).
• Biopsy is rarely needed for diagnosis. (ERS handbook 3rd ed.)

treatment and prognosis

• The prognosis is generally favorable.
• Treatment is rarely needed. Interventional pulmonology techniques may occasionally have a role to relieve endobronchial obstruction (e.g., laser treatment).

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respiratory papillomatosis

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basics

• Respiratory papillomatosis is due to papillomatous growths caused by human papilloma virus (HPV).
• The disease progression tends to progress downwards:
  • (#1) Laryngeal papillomatosis is the most common site of involvement, involved in ~95% of cases.
  • (#2) In 5% of patients, this spreads deeper to involve the trachea and/or proximal bronchi. Rarely, isolated tracheal involvement occurs. (34099155)
  • (#3) In <1% of patients, this progresses to involve the lung parenchyma.

epidemiology

• Respiratory papillomatosis is very rare.
• Adult-onset respiratory papillomatosis is spread via sexual transmission of human papillomavirus (HPV) (usually HPV-6 or HPV-11).
• Tracheal and parenchymal involvement usually presents among patients in their 30s-50s.

clinical manifestations

• Laryngeal involvement is most common; may cause:
  • Laryngitis, hoarseness.
  • Dysphagia.
  • Foreign body sensation in the throat.
• Tracheal/bronchial involvement may cause:
  • Stridor, wheeze, and dyspnea.
  • Recurrent pneumonia may occur if bronchial obstruction occurs, with eventual development of focal bronchiectasis.
• Malignant transformation into squamous cell carcinoma occurs in 2-3% of cases, usually within a decade of diagnosis. (34099155)

chest radiograph

• Papillomas usually aren't visible, but their effects on the airway may be notable.
• Findings on chest radiograph may include:
  • Atelectasis.
  • Mucus plugging (e.g., with a finger-in-glove sign).

CT scan

• Airway involvement
  • Multiple intraluminal polypoid nodules may occur in the trachea and proximal bronchi.
  • Postobstructive bronchiectasis may occur (figure below).
  • Lesions are not calcified. (Rosado-de-Christenson 2022)
  • (If a CT scan of the neck is performed, laryngeal papillomatosis may occasionally be seen.)
• Parenchymal lung involvement
  • Nodules occur initially, usually 1-3 cm in size. They tend to be multilobulated, well-defined, and noncalcified solid lesions. (34099155) 
    • ⚠️ Nodules may grow slowly, but any rapid growth is concerning for superimposed squamous cell carcinoma. (Rosado-de-Christenson 2022) 
  • Eventually cavitation can occur, yielding a 2-3 mm thick cavity with a nodular rim.
  • Lesions are typically located in the posterior half of the chest, in the dependent part of the lung. (Shepard 2019)

bronchoscopy

• Multiple nodules may be seen with variable locations along the vocal cord, trachea, and proximal bronchi. Alternatively, there may rarely be a single large papilloma.
• Biopsy may be performed if the diagnosis is unclear. (34099155)
• ⚠️ N95 masks should be used to prevent transmission to healthcare workers during bronchoscopy.

differential diagnosis

• Tuberculosis may cause laryngeal lesions resembling papillomas 📖, tracheal involvement, and cavitary lung lesions.
• Granulomatosis with polyangiitis may involve the larynx and trachea, sometimes with cavitary lung lesions.
• Tracheobronchopathia osteochondroplastica.
• Tracheobronchial amyloidosis.
• Relapsing polychondritis.
• Sarcoidosis.
• Superimposed squamous cell carcinoma (may complicate this condition).

treatment

• Lesions may be removed surgically (if on the larynx) or via interventional bronchoscopy (if on the trachea). Unfortunately, lesions often recur. Additionally, repeated airway procedures may increase the risk of airway stenosis or airway injury that further spreads the papillomas. Thus, intervention should be avoided unless there is clinically relevant airway obstruction. (Fishman 2023)
• Additional treatments may include subcutaneous interferon-alpha, bevacizumab, and intralesional cidofovir. The quadrivalent HPV vaccine (Gardasil™️) with activity against HPV 6, 11, 16, and 18 has been reported to cause improvement. (34099155) Unfortunately, there is little high-quality evidence regarding these.
• Serial imaging should be performed to surveil for malignant transformation. (34099155)

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relapsing polychondritis

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basics

• This is a rare systemic disorder characterized by episodes of inflammation of cartilaginous structures. Over time, widespread degeneration of cartilaginous structures occurs.

epidemiology

• Extremely rare overall.
• Peak onset is usually between 40-60 years old.
• Relapsing polychondritis is associated with a range of other disorders (especially connective tissue diseases).

clinical manifestations

• All cartilaginous structures may be involved (including ears, nose, peripheral joints, ribs, axial joints).
  • External ear pain may be the most common symptom, with ear involvement in ~90% of patients. The earlobe may be inflamed, erythematous, edematous, and tender. (33422236)
  • Nasal involvement occurs in half of patients (e.g., pain, erythema, and eventually a saddle nose deformity).
  • Ocular involvement may occur (conjunctivitis, scleritis, episcleritis).
  • Arthropathy occurs in half of patients.
  • Cardiac involvement may occur (including mitral or aortic regurgitation, or pericarditis).
• Respiratory involvement eventually occurs in about half of patients: (33422236)
  • Laryngeal involvement may cause hoarseness, aphonia, stridor, and/or choking.
    • Tenderness may occur over the thyroid and laryngeal cartilages. (Fishman 2023)
  • Tracheal involvement may cause dyspnea, dry cough, and/or stridor.
  • Flares may occur, with acute deterioration. Patients may be asymptomatic in between disease flares. (ERS handbook 3rd ed.)
  • Recurrent pneumonia is a common cause of death.

CT scan

• Diffuse, smooth thickening of the trachea and proximal bronchi.
  • Thickened (>2 mm), often densely calcified cartilaginous rings.
  • Posterior membrane is generally spared (since it doesn't contain cartilage). (29707497)
  • 💡 Diffuse, smooth thickening of the cartilaginous tracheobronchial tree that spares the posterior membrane is highly suggestive of relapsing polychondritis. Tracheobronchopathia osteochondroplastica 📖 also spares the posterior membrane, but it causes nodular thickening of the trachea.
• Airway collapse (due to loss of tracheal rings).
• Airway stenosis (due to tracheal wall edema, or strictures especially in the subglottic region). (Teneback 2022)
• Mosaic attenuation due to air trapping may be seen.
• Bronchiectasis may occur (due either to recurrent infection, or direct cartilage destruction). (Rosado-de-Christenson 2022)

laboratory studies

• Inflammatory indices may be elevated (e.g., erythrocyte sedimentation rate, C-reactive protein). (33422236)
• Peripheral eosinophilia can occur. (34295405)

bronchoscopy

• Findings may include:
  • Endobronchial inflammation.
  • Endobronchial stenosis.
  • Tracheobronchomalacia.
• Endobronchial biopsy is insensitive.
• ⚠️ Airway procedures carry a risk of acute airway compromise among patients with collapsible airways. (Murray 2022) Biopsy in particular should be avoided in the acute phase of the disease. (ERS handbook 3rd edition)

diagnostic criteria

• Diagnosis requires three or more of the following: (Murray 2022)
  • Bilateral auricular chondritis involving the cartilaginous pinna.
  • Nonerosive seronegative inflammatory polyarthritis.
  • Nasal chondritis.
  • Ocular inflammation.
  • Respiratory tract involvement (either upper or lower respiratory tract).
  • Cochlear involvement (with or without vestibular abnormality).
  • Positive biopsy specimen (noting that this traditionally has not been a diagnostic criterion).

differential diagnosis

• MAGIC syndrome: mouth and genital ulcers with inflamed cartilage (overlap of relapsing polychondritis plus Behcet disease).

treatment

• Steroid and immunosuppressive agents have been utilized, especially during acute disease flairs.
• Noninvasive positive pressure ventilation may help some patients with dynamic collapse of the upper airway. (Teneback 2022)
• Airway stenting may occasionally be helpful.
• Severe laryngeal edema may rarely necessitate emergent tracheostomy. (33422236)
• Cardiovascular involvement is the second leading cause of death, so echocardiography should be performed to evaluate for valvular dysfunction. (Rosado-de-Christenson 2022)

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tracheoesophageal fistula (TEF)

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epidemiology

• ~65% are due to malignancy:
  • Esophageal carcinoma most often.
  • Lung cancer.
• Chronic infection (tuberculosis, broncholithiasis due to histoplasmosis, actinomycosis).
• Radiation injury.
• Postsurgical.
• Status post mechanical ventilation or tracheostomy.

symptoms

• Cough triggered by eating or drinking.
• Recurrent aspiration and/or pneumonia.

diagnosis

• Barium esophagram:
  • Sensitivity isn't great, perhaps ~50%.
  • (Gastrografin should be avoided because it may cause chemical pneumonitis.)
• CT contrast esophagography may improve the yield: (Shepard 2019)
  • CT scan is performed before and after swallowing contrast dye (high-osmolar contrast should be avoided to reduce risk of pneumonitis).
  • CT may reveal the presence, site, and etiology of the fistula.
  • If the fistula isn't seen, other clues may include: (Shepard 2019)
    • Focal distension of the esophagus with air near the level of the fistula.
    • Signs of aspiration (e.g., tree-in-bud opacities)
• Bronchoscopy may show the fistula.

management

• Nonmalignant fistulas may be repaired surgically.
• Malignant fistulas may be palliated by stenting of the esophagus +/- airway.
  • Tracheal stenting may be especially useful if the fistula is accompanied by tracheal stenosis.
  • Stenting of both the trachea and the esophagus may increase the fistula size, while preventing it from healing. This should be avoided if possible, but may nonetheless be a necessary palliative measure in some patients with large fistulas. (Murray 2022)

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necrotizing tracheobronchitis

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basics

• An inflammatory process causes ulceration, necrosis, and sloughing of airway epithelium.

clinical presentation

• May cause cough.
• May cause large airway occlusion.

causes

• Bacterial infection (e.g., MRSA).
• Viral infection (e.g., HSV).
• Fungal infection:
  • Tracheobronchial aspergillosis 📖
  • Mucormycosis (especially among patients with diabetes). (28665704)
• Autoimmune disorders: (32252936)
  • Paraneoplastic pemphigus.
  • Inflammatory bowel disease

radiology

• Bronchial wall thickening may be seen.
• Airway occlusion may result in atelectasis or post-obstructive bronchitis.

bronchoscopy

• Inspection may reveal ulceration and necrosis.
• Tissue biopsy may evaluate for any localized infection.

differential diagnosis: other causes of tracheal necrosis/ulceration

• GPA (granulomatosis with polyangiitis). 📖
• Relapsing polychondritis. 📖
• Tuberculosis.

management

• (1) Any underlying etiology should be treated (e.g., infection).
• (2) Sloughing mucosa may need to be removed to maintain airway patency via interventional bronchoscopy (e.g., cryoextraction).

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obstructive fibrinous tracheal pseudomembrane (OFTP)

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basics

• Tracheal pseudomembrane forms due to traumatization of the trachea by an endotracheal tube. Over time, pseudomembranes may become partially detached.
• This is a rare condition, with unknown incidence.

clinical presentation

• Post-extubation respiratory distress and stridor is reported to occur between ~3 hours to 14 days after extubation. (25367484)

diagnosis

• Bronchoscopy will reveal the diagnosis (not laryngoscopy, as is often utilized to evaluate post-extubation stridor). Pseudomembranes appear as white, thick, tubular, and rubbery lesions that are firmly adherent to the tracheal wall. (25367484)
• CT scan may also be used, if the patient is sufficiently stable.

differential diagnosis: causes of pseudomembrane formation in the respiratory tract

• Inhalational injury, caustic burns.
• Aspiration of gastric contents.
• Infection: Staphylococcus aureus, Bacillus cereus, Aspergillus, Corynebacterium spp.

management

• Pseudomembranes should be removed via rigid bronchoscopy.

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sabre-sheath trachea

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radiological findings

• Primary, defining feature:
  • Coronal narrowing and sagittal widening of the intrathoracic trachea.
  • (Coronal dimension)/(Sagittal dimension) < ~0.66 (26912770)
• Initially may involve trachea at thoracic inlet, with eventual evolution to involve entire intrathoracic trachea. (Rosado-de-Christenson 2022)
• Tracheal cartilage may be calcified.
• Radiological differential diagnosis: (Rosado-de-Christenson 2022)
  • Tracheal stenosis.
  • Tracheobronchomalacia.
  • Diffuse tracheal narrowing (may be caused by infection, tracheobronchopathia osteochondroplastica, granulomatosis with polyangiitis, amyloidosis, relapsing polychondritis, or sarcoidosis).

causes

• Generally reflects chronic, severe obstructive airway disease:
  • COPD is the most common cause (this is a common finding in severe COPD). Saber sheath configuration of the trachea is ~95% specific for emphysema. (Rosado-de-Christenson 2022)
  • Reported in severe bronchiolitis obliterans.
• Rare causes:
  • Ankylosing spondylitis.
  • Tracheobronchopathia osteochondroplastica.

management implications

• Following intubation, this may lead to an air leak because the trachea doesn't match the circular configuration of the endotracheal cuff balloon.

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questions & discussion

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