Tc99m MDP bone scintigraphy including whole-body and spot “tail on detector” views demonstrates multiple skeletal lesions of increased activity that generally involve large segments of bone with associated cortical expansion. Long-segment lesions with cortical thickening are seen involving the pelvis. Another lesion starts at the extreme scapular tip. An entire lumbar vertebral level (anterior and posterior elements) is involved diffusely (“Mickey Mouse” sign; arrow).

Differential Diagnosis

•  Paget disease (PD): Multiple bone lesions, many with long segments and starting at the bone end or involving entire bones and with cortical expansion, make PD the most likely diagnosis.

•  Skeletal metastatic disease: This can look superficially similar to PD with multiple lesions. However, the lesions are usually more focal and do not cause cortical thickening. They are most commonly confined to the red marrow (i.e., more central) skeletal distribution, as (incidentally) seen in this case.