Presentation
Painful left hip.
Patient Data
Expansile bony lytic lesions with ground glass appearance and endosteal thinning of the cortex involving the supraacetabular region, femoral neck, proximal and mid-femoral diaphysis and tibial diaphysis. No periosteal reaction is seen.
No bony lytic lesion was seen in the right lower limb.
On the MRI sequences, the bony lesions elicit a low signal on T1 and T2, and an intermediate to high signal on STIR with moderate homogeneous enhancement.
The MRI exam was extended to the leg and showed another similar bony lesion of the tibial diaphysis.
Case Discussion
Radiographic and MRI features of multiple. Well-defined expansile bony lesions, highly suggestive of fibrous dysplasia (polyostotic form).
Fibrous dysplasia (FD) is a benign bony neoplasm (according to the WHO classification of tumors of bone, 5th edition) characterized by the failure to form mature lamellar bone and arrest as woven bone that can be multifocal.
There are two forms:
monostotic: more common, 70-80% of cases
polyostotic: less common, 20-30% of cases, often unilateral and monomelic (one limb), as in this case
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