Fig. 13.

Inflammatory disease. a 46-year-old male with history notable for hypertension, bilateral orbital xanthogranulomas, and chronic low-grade fevers. As part of work-up, the patient had an aortic MRI that demonstrated diffuse confluent soft tissue within the mediastinum (arrow). b There were additional soft tissue changes as well as stranding surrounding both kidneys (arrows). c FDG PET/CT showed only minimal FDG avidity in the paraaortic soft tissue. d FDG-PET/CT also showed only minimally increased uptake around the kidneys. Bone scan (not shown here) was notable for diffusely increased uptake along long bones. Given these imaging and clinical findings, chronic inflammatory process with suggestion of mild activity at time of imaging was suspected; laboratory testing of orbital biopsy (CD68, CD163 positive, CD1a negative) led to a diagnosis of Erdheim-Chester disease