Erdheim-Chester disease: symmetric uptake in the (99m)Tc-MDP bone scan.

Erdheim-Chester disease (E-C D) is a rare clinicopathologic entity with nearly pathognomonic radiographic features. About half of the affected exhibit extraskeletal manifestations, including involvement of the hypothalamus-pituitary axis, lung, heart, retroperitoneum, skin, liver, kidneys, spleen and orbit. This disease usually affects individuals in their fifties to their seventies and has a male preponderance.