Erdheim-Chester Disease

Erdheim-Chester disease, or non-Langerhan cell histiocytosis, is a disseminated xanthogranulomatous infiltration of unknown origin. Patients are typically in the 5th through 7th decades of life. The skeleton is most frequently affected, but up to 50% of patients have involvement of the lungs, central nervous system and retroperitoneum.

Erdheim-Chester disease predominantly involves the long tubular bones. The axial skeleton is less commonly affected.

On radiographs, there is symmetric diffuse or patchy medullary sclerosis or a coarsened trabecular pattern involving the diaphysis and metaphysis. The epiphysis is either spared or less severely affected. Cortical thickening can also be seen in the same distribution.

Bone or Gallium scintigraphy reveals symmetric bilateral uptake in the areas of radiographic abnormality.

MRI reveals replacement of normal marrow fat as low T1 signal and regions of low and high signal intensity on T2-weighted images. Contrast administration reveals heterogeneous enhancement with nonenhancing cystic components. We have also seen focal lesions with areas of internal fat.

The images above are from a 50-year-old man. The radiographs reveal symmetric patchy sclerosis in the long bones with cortical thickening in the distal femur. The bone scan reveals increased activity corresponding to the radiographic abnormalities.
May be considered in the differential diagnosis of fat-containing bone lesions.

References

Charest M, Haider EA, Rush C. An unusual cause of knee pain. Br J Radiol. 2007 Mar;80(951):227-9.