Tracheobronchial mucosal keratosis: A literature review of this rare disorder.

Background: Tracheobronchial mucosal keratosis (TBMK) is a rare airway disease that may cause refractory cough and airway stenosis. The characteristics of this disease remain unknown. In the present study, we describe this disorder based on a review of the current literature, emphasizing its diagnostic and therapeutic aspects. Methods: A comprehensive search of TBMK was performed in Medline, Google Scholar, Web of Science, Cochrane Library (UK), Embase, China National Knowledge Infrastructure (CNKI) (China), and Wan Fang Med Online (China). The following data were collected: patient characteristics, chest imaging findings, bronchoscopy, histopathologic findings, pathogen testing, treatment, and prognosis. Results: As of 2023, eighteen cases of TBMK have been reported. The main clinical manifestations were cough and expectoration. Chest imaging findings were non-specific. The main bronchoscopy findings were nodular protrusion of airway lumen and yellow-white purulent moss above the nodular lesion. The lesions were mainly located in the trachea and mainstem bronchus. The main pathological manifestations include keratinocytes or keratinocyte beads, squamous metaplasia, and mucosal inflammatory changes. The treatments that were administered include antibiotics, symptomatic treatment, and glucocorticoids. All methods were ineffective except for bronchoscopy-guided high-frequency electric knife and recombinant human epidermal growth factor treatment. Conclusions: TBMK is a rare respiratory disease with atypical clinical manifestations and chest computed tomography findings. Bronchoscopy revealed that nodular hyperplasia of the airway and purulent fur-covered lesions are typical manifestations. The final diagnosis needs to be confirmed by histopathological examination. There is a lack of effective treatment for this disease, and bronchoscopy-guided intervention therapy may be a candidate treatment.