Cover image: Figure 2 Plain radiograph of bilateral femurs, demonstrating a symmetrical pattern of long bone sclerosis typical for Erdheim-Chester disease. Figure 3 Erdheim-Chester disease. (A) Bone infiltration by histiocytic proliferation with osteosclerosis. (B) The histiocytes are both mononuclear and foamy.(see Dunkerton â€S, et al. page 92).