RESUMEN
BACKGROUND: Erdheim-Chester disease is a rare non-Langerhans' cell histiocytosis of unknown etiology with typical osteosclerotic long-bone findings. However, clinical symptoms are mostly due to disease involvement of other tissues, particularly of the lung, heart and retroperitoneum. CASE REPORT: A 58-year-old man presented with fatigue, diffuse pain of the lower extremities, dyspnea, and a dry cough. Physical examination was unremarkable. Chest X-ray revealed an extensive bilateral pulmonary inter interstitial process. Computed tomography demonstrated pulmonary fibrosis, periaortic fibrosis of the thoracic aorta, and retroperitoneal fibrosis. The diagnosis of Erdheim-Chester disease was confirmed by minimally invasive lung biopsy. Steroid therapy was not tolerated. Following a stable interval of 18 months there was a disease progression, which could be stabilized after the initiation of cyclophosphamide therapy. CONCLUSION: In patients with extensive pulmonary fibrosis and coincidence of other organ manifestations such as periaortic or retroperitoneal fibrosis and particularly in case of symmetrical osteosclerotic bone lesions, Erdheim-Chester disease should be considered. Immunosuppressive therapy can lead to a stabilization or even improvement of the disease.