[A case of pulmonary langerhans cell histiocytosis presenting disappearance of coalescing air wall cysts after smoking cessation].

A 17-year-old adolescent was admitted to Oita University Hospital with non-productive cough and exertional dyspnea. She had been smoking approximately 10 cigarettes per day for two years. When the patient was three years old, she underwent surgical removal of skull tumor of Langerhans cell histiocytosis. Initial chest CT scans showed coalescing thick-walled air cysts surrounded by micronodules in both lungs, most predominantly in the middle and upper lung fields. Bronchoalveolar lavage fluid contained 2.3% of CD1a-positive cells and video-assisted thoracoscopic lung biopsy disclosed granulomatous lesions consisting of histiocytic cells containing S-100 protein but without CD68 antigen allowing a diagnosis of pulmonary Langerhans cell histiocytosis. She stopped smoking, resulting in spontaneous resolution of the coalescing air cysts which were replaced by funicular scarring within two years. In case of extra-pulmonary Langerhans cell histiocytosis in children, the close relationship between cigarette smoking and pulmonary involvement should be informed to the parents to prevent the patient starting smoking in the future.