A rare case of "switch on and off" multi-system Langerhans cell histiocytosis in an adult patient

INTRODUCTION: We report the case of a 24-year-old Greek woman with histologically proven osseous and pulmonary Langerhans cell histiocytosis whose lesions had progressively regressed with a "switch on and off" mode. This is the first report in the literature of this mode of presentation of Langerhans cell histiocytosis. CASE PRESENTATION: The patient had first presented at the age of 20 years with a solitary lesion of the humerus which spontaneously regressed. At that time, no therapy or smoking cessation was indicated. Four years later she presented with bilateral pneumothorax and pulmonary lesions of Langerhans cell histiocytosis. She had pleurodesis for this disease-related complication, and no further systemic treatment was applied, except with regard to smoking cessation. During the follow-up period, her pulmonary lesions regressed without recurrence six years after the initial lung involvement. CONCLUSION: This uncommon case of remission of multi-system Langerhans cell histiocytosis indicates the unpredictable evolution of the disease, raising the question of conservative management in such a patient.