Magnetic resonance imaging of the leg in Erdheim-Chester disease

(A) T1.
(B) T2.
Magnetic resonance imaging of the left leg in a 48-year-old male with Erdheim-Chester disease shows abnormal signaling in the distal tibia with surrounding soft tissue edema. There is a heterogeneous signal in the bone marrow on T1 and T2 with areas of patchy enhancement post-gadolinium. The bone marrow signal abnormality extends more proximally than the lesion itself. There is a mild periosteal reaction, but no overt abnormality of true tumor extending out from the bone.