Erdheim-Chester disease: a rare cause of interstitial lung disease.

Erdheim-Chester disease is a non-Langerhans cell histiocytosis that is progressive and may lead on to multi-organ involvement. Pulmonary involvement is rare, its presentation is nonspecific, and it carries an adverse outcome. Several radiological features, when considered together, may point to the diagnosis. This condition should be considered in the differential diagnosis of interstitial lung disease. We describe a 39-year-old woman who presented with dry cough, malaise and progressive dyspnoea. She was diagnosed to have late stage interstitial lung disease due to Erdheim-Chester disease.