CTICasesErdheim-Chester Disease
Imaging findings
Initial chest radiograph demonstrates non-specific peripheral septal line thickening and mild thickening of the fissures. High-resolution CT of the chest confirms extensive interlobular septal thickening, mild ground-glass opacities, and thickened fissures without central adenopathy. Coronal and sagittal CT of the spine and pelvis reveals multiple sclerotic bone lesions, including prominent sacral sclerosis and a focal sclerotic lesion in the distal extremity. 18F-FDG PET-CT shows bilateral, symmetric increased radiotracer uptake in the long bones, specifically involving both femurs, proximal tibiae, and proximal humeri, while the sclerotic axial skeleton lesions remain metabolically quiescent.
Key takeaways
Erdheim-Chester disease is a rare, non-Langerhans cell histiocytosis that can present with unusual pulmonary findings mimicking interstitial lung disease or edema, such as smooth interlobular septal thickening and pleural/fissural thickening. While bone biopsies of sclerotic or quiescent lesions may occasionally be non-diagnostic or show burnt-out fibrosis without histiocytes, the diagnosis can be established by identifying characteristic BRAF mutations (such as BRAF V600E) in peripheral blood. The classic imaging signature of the disease is symmetric osteosclerosis of the long bones with intense FDG avidity on PET-CT.
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