Invasive aspergillosis is one of the most common fungal infections in immunocompromised hosts, involving the respiratory tract in 90% of cases. The most common form of aspergillus species infection in immunocompromised patients is invasive pulmonary aspergillosis, which mainly involves the lung parenchyma and, rarely, the trachebronchial tree.
Infection confined only to the tracheobronchial tree is known as invasive aspergillus tracheobronchitis (IATB), and it generally carries an ominous prognosis.
Three morpholgical variants of IATB have been described: obstructive tracheobronchitis, ulcerative tracheobronchitis and pseudomembranous necrotizing bronchial aspergillosis (PNBA). The obstructive form is characterized by massive intraluminal growth of aspergillus species associated with thick mucus plugs that generally produce atelectasis. Ulcerative lesions penetrate through the tracheo-bronchial wall, and can create bronchoesophageal or bronchoarterial fistulas that may produce fatal hemorrhage. PNBA is characterized by extensive formation of whitish pseudomembranes composed of hyphae, fibrin and necrotic debris. Rather than three distinct entities, these morphologic variants may just represent different stages in the development of IATB.
Huang et al classifed IATB into four different forms according to the bronchoscopic features of intraluminal lesions: superficial infiltration type(Type I), full-layer involvement type (Type II), occlusion type (Type III) and mixed type (Type IV). Type IV was the largest group in this study, followed by Type III. All patients with iIATB of Type IV had definite airway occlusion.
The clinical mainfestations of IATB are entirely different from those of invasive pulmonary aspergillosis. The insidious presentation with non-specific symptoms and the paucity of findings in chest roentgenograms often delay the diagnosis, giving this disease an ominous prognosis. Airway-related symptoms such as cough, dyspnea, wheezing and hemoptysis are cardinal features.
The diagnosis of IATB is almost always confirmed by bronchoscopic examination and sampling.
Voriconazole is currently the first-line agent for the treatment of invasive aspergillosis, since this second-generation triazole has been demonstrated to improve survival and result in fewer severe side effects than AmBD. The duration of therapy for AT must be individualized based on the clinical and radiologic response, as demonstrated by the notable heterogeneity we found in the present review (range, 8-307 d).
In conclusion, IATB is a rare form of invasive aspergillosis affecting mainly immunocompromised patients. The non-specific clinical presentation often leads to late diagnosis and poor prognosis.
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