In 1991, Kramer and coworkers proposed a classification of tracheobronchial aspergillosis in three types [2, 4]. The authors distinguished allergic, invasive, and saprophytic forms of aspergillus tracheobronchial involvement, similarly to pathogenesis of pulmonary aspergillosis. Allergic bronchopulmonary aspergillosis (ABPA) occurs in patients with normal immune function as antibody reactions (IgE and IgG) or cell-mediated immune responses (types I, III, IV hypersensitivity reactions). Invasive tracheobronchial aspergillosis (ITBA) occurs in patients with severe immunosuppression such as after organ transplantation or hematologic malignancies. Obstructing bronchial aspergillosis was first described by Denning et al. in three patients with AIDS [5]. This pathological feature was defined as the presence of thick mucous plugs containing aspergillus hyphae, with little or no airway inflammation and no evidence of invasion or allergic reaction. Obstructive bronchial aspergillosis is also known as endobronchial aspergillosis (EBA) [3]. It could not only cause obstructive pneumonia but be fatal by progression to invasive pulmonary aspergillosis (IPA) or forming tracheal-mediastinal fistula [3].
Though originally obstructive bronchial aspergillosis was reported to afflict patients with severe immunodeficiency, this time we experienced a case in an elderly outpatient without apparent immunosuppression. To elucidate patients’ backgrounds suffering from this, we performed comprehensive PubMed search for case reports of obstructive bronchial aspergillosis and found 34 cases [2] [4] [5] [6] [7] [8] [9] [10] [11] [12]. Their ages ranged from 28 to 76, but most of them were in their 60s and 70s. Only eight patients had severe immunodeficiency, such as AIDS, hematological malignancies, and post-transplantation. On the contrary, in 7 patients, no obvious backgrounds were described. The remaining 19 had some kind of comorbidity related with immunosuppression, including 4 with diabetes mellitus, 8 with solid tumors such as lung cancer, 7 with a history of tuberculosis, and 1 with rheumatoid arthritis. Among 10 of the 19 patients had multiple such complications. Our review demonstrated that more common patients than previously thought might have a risk of this disease, though the incidence is very low. In our case, in addition to maintained cytotoxic chemotherapy and old age, inhaled steroid therapy for asthma might have a certain role as it is often reported to cause infection such as oral candidiasis or bacterial pneumonia via direct immunosuppressive effects [13].
Initial symptoms are non-specific and included asymptomatic, cough, hemoptysis, dyspnea, malaise, weight loss, chest pain, and fever [3] [9]. On a chest X-ray or CT, this appears as a nodular shadow or bronchial obstruction. PET-CT seems to be able to exclude the possibility of malignancy such as lung cancer as this shows low upkate of FDG [1] [3]. Bronchoscopy is essential for diagnosis. Typical finding by bronchoscopy is an increased white necrotic material obstructing the bronchi observed in this case, and definitive diagnosis is a presence of hyphae. Currently, no standard treatment for this has not been established, while, as performed in this case, antifungal drugs such as voriconazole (VRCZ), itraconazole (ITCZ), and micafungin (MCFG), and direct debridement of the abscess by bronchoscopy are thought to be two major treatment options [3].
In conclusion, it is likely that obstructing bronchial aspergillosis could occur in much more common patients with pulmonary diseases. When obstructive lesions are found on imaging tests in aged patients along with respiratory symptoms, physicians should consider this disease as one of differential diagnoses, and bronchoscopy should be actively performed for detecting the existence of hyphae.