This case shows the typical appearance of lytic phase Paget disease of the femur on x-ray, CT, MRI and bone scan. This lesion was incidentally detected as part of a work-up for total hip replacement. The classic blade of grass sign (candle flame appearance) was not appreciated by the initial reader of the x-ray and instead an aggressive process such as metastasis or myeloma was suggested. The initial reader of the CT also suggested metastasis or myeloma as the likely diagnosis despite the fat density of the marrow being preserved. It was not until the MRI study was read that the correct diagnosis of lytic phase Paget disease was made.

General teaching points

• bone lesions can often have distinguishing diagnostic features on x-ray
• don't forget that CT can be useful in assessing the presence or absence of fat density within marrow
• T1 weighted MRI and recognition of preserved fat signal is critical in the assessment of bone lesions