The diagnosis of OATB can be safely made with microbiologic isolation of Aspergillus species from aspirated mucus or sputum in the absence of clinical features of asthma, central bronchiectasis, and pulmonary infiltrates, all of which point to allergic bronchopulmonary aspergillosis (ABPA). Higher attenuation of mucus with a typical finger-in-glove appearance is characteristic of ABPA. Although endobronchial mucosal biopsies to rule out invasion would be ideal in differentiating OATB from other forms of ATB, this patient did not have the airway abnormality typically seen in invasive tracheobronchitis for targeted sampling. More importantly, initial antifungal therapy would not be altered by the results of endobronchial biopsies. Patients with OATB do not meet the diagnostic criteria for ABPA, such as central bronchiectasis, positive Aspergillus precipitins, elevated IgE, symptoms of asthma, and infiltrates among others. Galactomannan in serum and bronchial washings are more likely to be positive in OATB but not in ABPA. Overall, serologic testing, when coupled with clinical history and imaging, can help clinch the diagnosis. First reported by Denning and colleagues in 1991 in a patient with HIV infection, OATB has been reported subsequently in patients after heart or lung transplant.