F-18 FDG PET/CT for detecting bone and bone marrow involvement in sarcoidosis patients

The prevalence of bone involvement in sarcoidosis has been estimated to be 3% to 5%, mostly affecting the phalanges. The aim of this study was to assess the prevalence and distribution pattern of bone and bone marrow involvement as detected by positron emission tomography/computed tomography (PET/CT) in sarcoidosis patients.

Between June 2006 and September 2010, 122 patients suffering from severe sarcoidosis who underwent a PET/CT and met the inclusion criteria were studied. In 94 (77%) patients, the PET/CT demonstrated positive findings associated with sarcoidosis. The 94 PET/CTs were screened for the presence of bone/bone marrow localizations. Additionally, low-dose CT scans were screened for other causes of increased bone uptake. Relevant clinical data were gathered retrospectively.

Evidence for bone/bone marrow localizations was found in 34% of the 94 patients with PET/CT-positive findings. Of these patients, 60% showed obvious focal bone lesions at various localizations: axial skeleton (47%), pelvis (40%), extremities (34%), and skull (2%). In 40% of patients, diffuse increased uptake in both axial and peripheral bone marrow, without focal lesions, was found. Both diffuse and focal uptake were seen in 34%, whereas only focal lesions were observed in 25%. In all but 2 (6%) patients, no bone abnormalities on low-dose CT were found.

More than one-third of PET/CT-positive sarcoidosis patients had osseous abnormalities on PET/CT. The majority of these lesions (94%) could not be detected on low-dose CT. No single localization of preference was found. These preliminary results stress the value of PET/CT imaging in the assessment of bone/bone marrow involvement in sarcoidosis patients.