This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
[{'content': 'After suffering a respiratory tract infection, a 64-year-old female biochemist develops chronic lung disease requiring intubation in the ICU for an 8-week period. Tracheal stenosis is noted. What is the most likely cause of tracheal stenosis? \nSelect and explain. \nA. Prolonged intubation, B. Tuberculosis, C. Scleroderma, D. Riedel struma (fibrous thyroiditis)', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Any object that compromises the blood supply to the tracheal mucosa or cartilage can cause stenosis. When the mean intramural pressure exceeds 20-30 mm Hg, damage may be anticipated. Riedel struma is a rare fibrosing thyroid condition, which must be differentiated from carcinoma and may cause severe tracheal stenosis. Achalasia is a neuromuscular defect at the lower end of the esophagus causing dysphagia, because of nonmechanical esophageal obstruction.', 'role': 'assistant'}]