Imaging in Erdheim-Chester disease: classic features and new insights.

Erdheim-Chester disease is a rare non-Langerhans cell histiocytosis. Osseous involvement is the most frequent feature with bilateral and symmetric osteosclerotic changes in long bone diaphyseal and metaphyseal regions, classically sparing epiphyses. 99mTc scintigraphy shows bilateral and symmetrical metaphysal and diaphyseal increased uptake in almost all the patients, even asymptomatic. Other classical features on CT-scan, very evocative of Erdheim-Chester disease, must be recognised: e.g. 'coated' aorta, 'hairy kidney' patterns. New imaging techniques such as MRI have led to a better description of cardiac and central nervous system involvements. Pachymeningitis and right atrium wall infiltration are new evocative images of this disease. Fluorodeoxyglucose Positron Emission Tomography in the diagnosis or prognosis assessment is still discussed. The objective of this review is to discuss the place of each imaging technique in Erdheim-Chester disease in 2013.