Fibrous Dysplasia¶
Overview¶
Fibrous dysplasia is a developmental disorder in which normal bone is replaced by fibrous tissue and immature woven bone. Spinal involvement is uncommon (<5% of cases). It may be monostotic (70%) or polyostotic (30%). McCune-Albright syndrome includes polyostotic fibrous dysplasia, café-au-lait spots, and precocious puberty.
Imaging Findings¶
CT (Best Modality)¶
- Ground-glass matrix — The hallmark finding. Homogeneous, hazy, intermediate-density matrix within an expanded bone, resembling ground glass.
- Expansile lesion with smooth, well-defined margins
- No periosteal reaction (unless fractured)
MRI¶
- Variable signal — often low to intermediate on T1 and T2 (fibrous content)
- Enhancement is variable
- Can mimic other lesions on MRI — CT is more diagnostic
Clinical Pearl
Ground-glass matrix on CT is the hallmark of fibrous dysplasia and is the key to the diagnosis. On MRI, the fibrous tissue can produce low T2 signal that may be confused with sclerotic metastasis. When an indeterminate vertebral lesion has ground-glass density on CT, fibrous dysplasia should be the leading diagnosis.
Key Points¶
- Ground-glass matrix on CT is diagnostic
- Spinal involvement is uncommon (<5%)
- Monostotic (70%) vs polyostotic (30%)
- McCune-Albright syndrome: polyostotic FD + café-au-lait + precocious puberty
- MRI signal is variable and often nonspecific — CT is more diagnostic
References¶
- Kushchayeva YS, Kushchayev SV, Glushko TY, et al. Fibrous dysplasia for radiologists: beyond ground glass bone matrix. Insights Imaging. 2018;9(6):1035-1056. https://pmc.ncbi.nlm.nih.gov/articles/PMC6269335/
- Park SK, Lee IS, Choi JY, et al. CT and MRI of fibrous dysplasia of the spine. Br J Radiol. 2012;85(1015):996-1001. https://pubmed.ncbi.nlm.nih.gov/22167510/
- Fitzpatrick KA, Taljanovic MS, Speer DP, et al. Imaging findings of fibrous dysplasia with histopathologic and intraoperative correlation. AJR Am J Roentgenol. 2004;182(6):1389-1398. https://pubmed.ncbi.nlm.nih.gov/15149980/
- Javaid MK, Boyce A, Appelman-Dijkstra N, et al. Best practice management guidelines for fibrous dysplasia/McCune-Albright syndrome: a consensus statement from the FD/MAS international consortium. Orphanet J Rare Dis. 2019;14(1):139. https://pubmed.ncbi.nlm.nih.gov/31196103/
- Tafti D, Cecava ND. Fibrous Dysplasia. In: StatPearls. Treasure Island (FL): StatPearls Publishing; updated 2023 Jul 24. https://www.ncbi.nlm.nih.gov/books/NBK532947/
- Fibrous dysplasia. Radiopaedia.org. https://radiopaedia.org/articles/fibrous-dysplasia