Erdheim-Chester disease presenting with pneumothorax.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis most commonly characterized by symmetrical skeletal involvement and may present with pulmonary involvement leading to chronically progressive pulmonary symptoms. Characteristics on chest radiography include non-specific findings of diffuse interstitial and pleural thickening, micronodules, ground-glass opacities and parenchymal condensation as a result of infiltration by lipid-laden histiocytes. We present the case of a 50-year-old man with ECD presenting with acute pulmonary symptoms due to rupture of a large cystic lesion with resultant pneumothorax. He was brought by ambulance to our hospital, complaining of acute anterior chest pain and severe dyspnea. Chest radiography showed right-sided pneumothorax with a collapsed lung, a large, left-sided cystic lesion in the upper lung field and accentuated interstitial markings. Bullectomy and surgical biopsy were performed, demonstrating histologically histiocytic infiltrates that were strongly positive for CD68, but negative for S-100 protein and CD1a. Subsequent systemic examinations indicated widespread symmetrical skeletal involvement, leading to a definitive diagnosis of ECD.