The role of 18FDG, 18FDOPA PET/CT and 99mTc bone scintigraphy imaging in Erdheim–Chester disease

Highlights: • Erdheim–Chester disease (ECD) is a rare non-Langerhans cell histiocitosis, characterized by multisystemic xanthogranulomatous infiltration by foamy histiocytes. Etiology and pathogenesis are still unknown and only about 500 cases are related in the literature. • Multifocal nature of involvement in ECD can produce a wide variety of clinical signs. In our experience, neurological involvement is associated with mortality in all cases. Characteristic long bone osteosclerosis was a quasi-pathognomonic finding in bone scintigraphy. • To the best of our knowledge, the 18FDOPA-PET/CT not seem useful in the initial staging of ECD based on a single case report. • Bone scintigraphy and the 18FDG-PET/CT that were particularly useful in despite systemic involvement, locate the optimum site for biopsy and treatment response evaluation. In this context, a baseline 18FDG-PET/CT with an optional bone scintigraphy may help in monitoring the disease and could be considered when patients were incidentally diagnosed and periodically follow-up 18FDG-PET/CT must be performed in the follow up to evaluate the treatment response. - Abstract: Erdheim–Chester disease (ECD) is a rare non-Langerhans cell histiocitosis, characterized by multisystemic xanthogranulomatous infiltration by foamy histiocytes that stain positively for CD68 marker but not express CD1a and S100 proteins. Etiology and pathogenesis are still unknown and only about 500 cases are related in the literature. Multisystemic involvement leads to a wide variety of clinical manifestations that results in a poor prognosis although recent advances in treatment. We present the clinical, nuclear medicine findings and therapeutic aspects of a serie of 6 patients with histopathological diagnosis of ECD, who have undergone both bone scintigraphy (BS) and 18F-fluorodeoxyglucose (18FDG)-PET/CT scans in our institution. A complementary 18F-fluorodopa (18FDOPA)-PET/CT was performed in one case. Three different presentations of the disease were observed in our casuistic: most indolent form was a cutaneous confined disease, presented in only one patient. Multifocal involvement with central nervous system (CNS) preservation was observed in two patients. Most aggressive form consisted in a systemic involvement with CNS infiltration, presented in three patients. In our experience neurological involvement, among one case with isolate pituitary infiltration, was associated with mortality in all cases. 18FDG-PET/CT and BS were particularly useful in despite systemic involvement; locate the site for biopsy and the treatment response evaluation. By our knowledge, 18FDOPA-PET/CT not seems useful in the initial staging of ECD. A baseline 18FDG-PET/CT and BS may help in monitoring the disease and could be considered when patients were incidentally diagnosed and periodically 18FDG-PET/CT must be performed in the follow up to evaluate treatment response