DISCUSSION
These case reports demonstrate that patients with cough, chest tightness and fever may have inflammation of the trachea and main bronchi without abnormalities in other organs, which can constitute the pathogenesis of various clinical conditions. Previous reports have presented some cases of inflammation of the trachea and main bronchi with abnormalities in the lung and/or other organs, such as a case of IgG4-related disease [3-5] and a case of granulomatosis with polyangiitis [6,7]. However, there is no past report on inflammation localized to the trachea and main bronchi. We referred to this presentation as tracheobronchitis in the title because these three cases presented with lesions confined to the trachea and main bronchi.
In this series, CASE 1 showed eosinophilic and plasmacytic infiltration based on bronchial biopsy specimens, suggesting an allergic mechanism. For CASE 2, mild IgG4-positive plasmacytic infiltration based on bronchial biopsy specimens was observed, indicating possible localized IgG4-related disease. However, this is not definitive because IgG4-positive cells are also present in other diseases, such as vasculitis. CASE 3 exhibited palisading granuloma and multinucleated giant cells in the bronchial biopsy specimens, which led us to suspect a subtype of localized granulomatosis with polyangiitis. Although inflammation of the central airway was observed in all three cases, there is a distinct possibility that these three diagnoses had different underlying mechanisms.
Previously, it was not commonly considered that inflammation of the large airways would produce such diffuse wall thickening. However, in this report, we show that tracheobronchitis can cause various types of inflammation with wall thickening. It is suspected that tracheobronchitis is not a rare condition; however, it is likely less noticeable. More attention should be paid to the wall of the trachea and main bronchi during the interpretation of chest CT findings in patients with chest symptoms or fever to fully understand their clinical condition. If thickening of the airway wall is detected, we should investigate the cause of thickening with bronchial or tracheal biopsy using flexible bronchoscopy. The pathological findings in the biopsy tissue can reveal large airway conditions in these patients and guide appropriate treatment strategies.
We hope that additional cases with similar findings are reported in the future to further our understanding of this clinical condition.