[Pulmonary Langerhans cell histiocytosis in identical twins].

Case 1 was a 22-year-old younger sister of identical twins who had smoked 10 cigarettes per day for 4 years since she was 18. She was admitted to our hospital due to dyspnea on exertion, dry cough and bilateral diffuse reticulonodular infiltrates on chest computed tomography (CT). Histological findings of transbronchial lung biopsy demonstrated nodular lesions consisting of spindle-shaped mononuclear cells. Immunohistochemical studies revealed that the cytoplasm of these mononuclear cells showed positive reactions to CD1a. Based on these findings, she was given a diagnosis of pulmonary Langerhans cell histiocytosis (LCH). She reduced the number of cigarettes smoked to 1 cigarette per week. After 6 months, her respiratory symptoms and radiographic abnormalities had improved. Case 2 was the elder twin sister of case 1. She had smoked 5 cigarettes per day for 4 years since she was 18. She presented no respiratory symptoms. However, as the diagnosis in case 1 was LCH, a chest CT was taken which revealed 3 small nodular lesions. After six months, there were no significant changes on chest CT. At the time of writing, she is 23-years-old and continues to smoke, however, has no respiratory symptoms.