[Erdheim-Chester disease: normal skeletal radiography in a patient with extensive bone involvement].

Erdheim-Chester disease is a rare disorder of unknown cause, characterized by systemic histiocytic infiltration; the long bones of the limbs are usually affected symmetrically, and a direct radiography of the involved skeletal segments is able to show a pattern of typical abnormalities. However, the patient we describe suffered of serious clinical symptoms in the lower limbs, but the direct radiography of the legs did not show any abnormality; this finding seems very remarkable and, to our knowledge, has not been reported previously in the literature. Therefore we discuss the role of the imaging procedures in the diagnosis of Erdheim-Chester disease. Differently from other authors, we did not obtain any clinical improvement in our patient by steroid treatment alone, that is generally considered the first therapeutic option for Erdheim-Chester disease with only skeletal involvement.