Non-sclerotic bone involvement in Erdheim-Chester: PET/CT and MRI findings in a 15-year-old boy.

Erdheim-Chester disease is a rare form of non-Langerhans cell histiocytosis with multi-organ infiltration that occurs mainly in adults. Pediatric cases are extremely rare. Here we report a case of multisystemic Erdheim-Chester disease in a 15-year-old boy with central nervous system involvement and skeletal findings. Positron emission tomography (PET) and MRI were used to demonstrate characteristic bilateral, symmetrical medullary involvement of the metadiaphyses of long bones in the absence of the classic sclerotic radiographic appearance. This illustrates the potential for earlier diagnosis and visualization of therapeutic response in children.