Introduction:
The patency of the airway tract is necessary for successful air conduction. However, in certain cases, airway patency is lost due to pathological changes. Amyloidosis is a rare disorder in which airway patency is lost due to protein deposition. It is a rare disorder. Only one person in 1000000 individuals is affected by this condition. Also, the long-term survival rate in this condition is less.
What Is Amyloidosis?
This is a heterogeneous disorder characterized by the deposition of protein-like substances in different tissues. In this type, proteins can be deposited in various organs like the heart, kidney, spleen, nerves, and lungs. The protein molecules that are deposited on the tissue surface are toxic and insoluble beta-sheet fibrillar protein aggregates.
The exact cause or pathogenesis of amyloidosis is not known. However, this is associated with protein formation disorders. Proteins are called the bundle of life. In this condition misfolding in the protein synthesis is responsible for the generation of abnormal protein molecules. These molecules are carried through the blood vessels and are deposited in several parts of the body. On the basis of the type of proteins that are found in this disease, this can be categorized into several types. These are:
-
Amyloid Light Chain (AL Amyloidosis or Primary Amyloidosis): In this type of amyloidosis plasma cells of the bone marrow have abnormal protein molecules. These plasma cells produce excessive amounts of immunoglobulin (Ig). In this type, the proteins are light chain type either kappa or lambda variant, and are deposited in various organs. This can be both localized and systematic type.
-
Amyloid Serum A protein (AA Amyloidosis or Secondary Amyloidosis): In this type, the proteins of the amyloidosis are synthesized in the liver. Inflammatory mediators like interleukin-1 beta and tumor necrosis factor help in this process. This is associated with disorders like rheumatoid arthritis and inflammatory bowel disorder.
-
Amyloid Transthyretin Protein or TRR Protein (ATTR Amyloidosis or Transthyretin Amyloidosis): This is also called hereditary amyloidosis. In this type, defective formation and deposition of transthyretin protein can be seen. Cardiac involvement is common in this type.
What Is Tracheobronchial Amyloidosis?
The tracheobronchial amyloidosis is a rare phenomenon. It is considered a rare subtype of pulmonary amyloidosis. Only 132 published cases have been identified so far. Women are more commonly affected by this condition than men. The larynx and trachea are most commonly involved.
1. Risk Factors:
Smoking and chronic obstructive pulmonary disorder are considered potential risk factors for this condition. Smoking and chronic obstructive pulmonary disorder is responsible for chronic inflammation of the lungs. In such cases, infiltration of chronic inflammatory cells such as monocytes and macrophages. These cells are secret precursor proteins responsible for the synthesis of the amyloidosis protein.
2. Symptoms:
The symptoms of tracheobronchial amyloidosis are:
-
Shortness of breathing and respiratory difficulties can be observed.
-
The patient complains of a cough and blood with sputum.
-
Respiratory sounds like wheezing can be present because of the narrowing of the airway tract.
The diagnostic findings are:
-
In most cases, radiographic findings are non-specific. Narrowing of the airway tract and collapse of the lung structure can be seen in some cases.
-
Computed tomography imaging is the most authentic diagnostic technique for this disease. Mucosal thickening of the trachea can be observed. Most commonly, the posterior membrane of the trachea is involved. Calcification in the bronchi and trachea can also be observed. Nodular and diffuse opacities can be identified.
-
In the bronchoscopy evaluation multiple white, diffuse plaque-like deposits can be seen. These deposits block the airway lumen completely. These deposits are mainly observed in the posterior wall. These deposits are fragile and are limited to the submucosa and blood vessels. During biopsy or bronchoscopy slight injury to these areas may cause bleeding.
3. Types:
Based on the involvement of the airway this can be divided into proximal, mid, and distal disorders. On the basis of radiographic findings in the lungs, this can be divided into nodular and diffuse types. In the nodular type smooth contours are observed in the subpleural region. The reticular and reticulonodular pattern of opacities can be found in the diffuse type. In this type, peripheral alveolar opacities can also be seen.
4. Diagnosis:
Based on radiological and bronchoscopy evaluation preliminary diagnosis is done. Confirmatory diagnosis is done based on the evaluation of biopsy sampling. Congo red staining is used to identify amyloid deposits. These deposits appear as bright orange areas and in the polarized microscopy, they appear as apple-green birefringence areas. Electrocardiograms and echocardiograms can be used to determine cardiac involvement in these cases. Fat pad aspiration and staining with congo-red can be used serum and urine sample electrophoresis with immunofixation and free light chain analysis can be done for ruling out plasma cell dyscrasia. Mass spectrometry is the gold standard test to identify amyloid protein analysis. Other methods of direct testing involved in this case are, staining with potassium permanganate and immunohistochemical staining of kappa and lambda chain can also be used. These methods are useful in identifying different proteins involved in such cases.
What Are the Radiographic Characteristics of Tracheobronchial Amyloidosis?
-
Standard Radiographs: Plain film results are challenging, frequently general, and in as many as 25 percent of cases, they can appear to be normal. The tracheal lumen may constrict irregularly and may have a nodular appearance. Because of endobronchial blockage brought on by amyloid deposition, lobar or segmental collapse could be observed as a subsequent characteristic.
-
Computed Tomography: Possible symptoms include mucosal thickening and calcification in areas of the trachea and bronchi. Narrowing the damaged sections of the airway is another option. Classically, the posterior membrane also has an impact when it affects the trachea. Moreover, CT is thought to help determine the extent of illness. Either a localized or extensive illness distribution is possible.
What Are the Differential Diagnosis of Tracheobronchial Amyloidosis?
It includes the following -
-
Tracheobronchopathia osteochondroplastica (an uncommon, benign tracheobronchial illness with an unclear cause).
-
Relapsing polychondritis (the condition is defined by repeated inflammation and swelling of the body's tissues, including cartilage).
-
Granulomatosis with polyangiitis (an uncommon autoimmune illness that results in organ and blood vessel inflammation).
-
Post-intubation tracheal stenosis (tracheostomies, which are surgical incisions made in the trachea that can be temporary or permanent, can cause individuals to experience tracheal stenosis, a constriction of the trachea).
What Are the Treatment Options?
The treatment option in such cases is based on the extent of the disease. Chemotherapy can be used in the treatment of systemic involvement. For localized involvement debridement of the protein deposits can be done with the help of forceps and lasers. Proximal disease involvement required more frequent debridement than mid-bronchial involvement. External beam radiotherapy can also be used in such cases to suppress the clonal B-cells within the tissue. Supportive therapy like antibiotics, nebulizer therapy, and administration of systemic or inhaled steroids can be continued.
Conclusion:
Amyloidosis is an extremely rare disorder. Deposition of defective protein in various organs is seen in this condition. Tracheobronchial involvement is an extremely rare condition and it is a subtype of pulmonary involvement. Proper investigation and laboratory examinations are important for the diagnosis of this condition. Though a proper cure for this disorder is not available, a procedure like laser debridement, chemotherapy, and radiotherapy can be useful in increasing the life expectancy of the patient.
