Favorable radiological outcome of skeletal Erdheim-Chester disease involvement with anakinra.

Erdheim-Chester disease is a rare non-langerhans cell histiocytosis characterized by infiltration of foamy CD68-positive but CD1a-negative macrophages and fibro-inflammatory lesions as retroperitoneal, periureteral areas or bones. Interferon-α therapy has been used as treatment but it had variable efficiency and limited tolerance. More recently, a recombinant form of interleukin-1 receptor antagonist (anakinra) was used with success but no skeletal radiological improvement was recorded. We report here a case of interleukin-1 receptor antagonist in the treatment of refractory bones infiltration in Erdheim-Chester disease. After 1 year of treatment, the positron emission tomography-computed tomography showed an outstanding response of the skeletal involvement with clearly lower and smaller hypermetabolism images.