Fibrous dysplasia is also known as Jaffé-Lichtenstein disease and is a congenital disorder of ossification. It consists of non-neoplastic lesions in which bone is partially replaced by connective tissue1. Due to the poor-quality substantia compacta, the bone is expanded, deformed, and at risk of fracture.
Epidemiology
The true incidence is unknown, as many of the lesions are asymptomatic. Fibrous dysplasia accounts for approximately 7% of benign bone lesions2.
Location
Lesions caused by fibrous dysplasia most commonly occur in the ribs, proximal femur, and craniofacial region, with the maxilla being particularly frequently affected3.
Malignant Transformation
Malignant transformation has been described in < 1 % of cases. Typically, malignant transformation is into an osteosarcoma, although other sarcoma types are also possible4. Radiation therapy can increase the risk of malignant transformation by up to 44% and is therefore considered relatively contraindicated5 6.
Morphological Classification
Depending on the morphology, three different types of fibrous dysplasia can be distinguished in the skull7:
- Cystic (although cystic is not meant in the classic sense here): Enlargement of the diploë with thinning of the outer table and little involvement of the inner table. Typically occurs in the calvaria.
- Sclerotic: Typically affects the skull base, particularly the Os sphenoidale and the facial bones.
- Mixed: The lesion resembles the cystic type, with areas of increased density within the lesion.
Imaging
Lesions of fibrous dysplasia can be visualized on MRI or CT imaging.
Associated Diseases
Fibrous dysplasia is part of McCune-Albright syndrome.
References
Handbook of Neurosurgery. Greenberg M, ed. 9th Edition. New York: Thieme; 2019 ↩ ↩ ↩ ↩ ↩ ↩
Parekh, Selene G., et al. "Fibrous dysplasia." JAAOS-Journal of the American Academy of Orthopaedic Surgeons 12.5 (2004): 305-313. ↩ ↩
Lee JS, FitzGibbon EJ, Chen YR, et al. Clinical guidelines for the management of craniofacial fibrous dysplasia. Orphanet J Rare Dis. 2012;7 Suppl 1:S2-S2 ↩ ↩
Bibby, K., and R. McFadzean. "Fibrous dysplasia of the orbit." British journal of ophthalmology 78.4 (1994): 266-270. ↩ ↩
Dumont, Aaron S., et al. "Cranioorbital fibrous dysplasia: with emphasis on visual impairment and current surgical management." Neurosurgical focus 10.5 (2001): 1-8. ↩ ↩