Fibrous dysplasia
Objectives- Describe differing patterns of involvement noted
in patients having fibrous dysplasia of bone
- Describe the pathology of fibrous dysplasia
- Discuss the genetic anomalies associated with fibrous
dysplasia
- Discuss the natural history and results of treatment of bony deformity secondary to fibrous dysplasia
Discussion points
- What bones are most often affected with fibrous
dysplasia?
- Why is fibrous dysplasia so difficult to treat effectively?
Discussion
Fibrous dysplasia is an annoying and intriguing benign bone lesion. It is not a neoplasia, but a developmental abnormality. It can present in a monostotic or polyostotic form. The polyostotic form generally is more severe and tends to be unilateral, the monostotic is fortunately more common. Albright's syndrome consists of cutaneous pigmentation, polyostotic fibrous dysplasia, and precocious puberty in girls. Other endocrine abnormalities have been noted with the polyostotic form. Fibrous dysplasia overall has a slight female preponderance. Radiographically, the appearance is somewhat variable. The lesion is usually diaphyseal. The cortex is expanded, with the "ground glass" appearance of the medullary canal. Calcification may be present. Radionuclide scans are markedly positive, out of proportion to the radiographic appearance. Microscopically, fibrous dysplasia has a very characteristic appearance, with irregular strands of osteoid and bone in a background of fibrous tissue. The lesions of fibrous dysplasia are difficult to treat. Curettage is ineffective, especially in childhood. If cancellous graft is placed, it will be absorbed. Enneking and Gearen recommended replacement of the lesion with cortical allograft, which would resist absorption by the host bone and provide structural stability. Guile noted that the lesion never healed, and the only way to improve function
was with valgus osteotomy of the proximal femur to improve the biomechanics, essentially ignoring the lesion. Vascularized bone grafting has been reported as effective for lesions of the upper limb.
Fibrous dysplasia is of interest from a genetic standpoint, because it appears to be a somatic mutation, in that the mutation occurs after fertilization in some subsequent cell division. The site of the mutation has been located, the gene for the alpha subunit of stimulatory guanine-nucleotide-binding protein, a protein that stimulates cyclic adenosine monophosphate is mutated. This defect has been found both in polyostotic and monostotic forms of fibrous dysplasia. The ultimate therapy for fibrous dysplasia will very likely be derived from recombinant protein resulting from further investigation of the genetic control of this condition. Pamidronate has recently been shown to have a beneficial effect on the ability to successfully instrument bony lesions of fibrous dysplasia associated with McCune-Albright syndrome. Malignancy has been documented in about 2% of cases followed at the Mayo clinic. Prior radiation was associated with some, but not all of the lesions. Radiation therapy does not appear to be a logical treatment at present.
References
- Bianco P, Riminucci M, Majolagbe A, Kuznetsov SA, Collins MT, Mankani MH, et al. Mutations of the GNAS1 gene, stromal cell dysfunction, and osteomalacic changes in non-McCune-Albright fibrous dysplasia of bone. Journal of Bone & Mineral Research 2000; 15( 1): 120-8.
- Enneking WF, Gearen PF. Fibrous dysplasia of the femoral neck. Treatment by cortical bone-grafting. Journal of Bone & Joint Surgery -American Volume 1986; 68( 9): 1415-22.
- Fisher AJ, Totty WG, Kyriakos M. MR appearance of cystic fibrous dysplasia. Journal of Computer Assisted Tomography 1994; 18( 2): 315-8.
- Guille JT, Kumar SJ, MacEwen GD. Fibrous dysplasia of the proximal part of the femur. Long-term results of curettage and bone-grafting and mechanical realignment. Journal of Bone & Joint Surgery -American Volume 1998; 80( 5): 648-58.
- Kumta SM, Leung PC, Griffith JF, Kew J, Chow LT. Vascularised bone grafting for fibrous dysplasia of the upper limb. Journal of Bone & Joint Surgery -British Volume 2000; 82( 3): 409-12.
- Lala R, Matarazzo P, Bertelloni S, Buzi F, Rigon F, de Sanctis C. Pamidronate treatment of bone fibrous dysplasia in nine children with McCune-Albright syndrome. Acta Paediatrica 2000; 89( 2): 188-93.
- Riminucci M, Liu B, Corsi A, Shenker A, Spiegel AM, Robey PG, et al. The histopathology of fibrous dysplasia of bone in patients with activating mutations of the Gs alpha gene: site-specific patterns and recurrent histological hallmarks. Journal of Pathology 1999; 187( 2): 249-58.
- Ruggieri P, Sim FH, Bond JR, Unni KK. Malignancies in fibrous dysplasia. Cancer 1994; 73( 5): 1411-24.
- Simon MA, Springfield DS. Surgery for bone and soft tissue tumors. Philadelphia: Lippincott-Raven; 1998.
- Zacharin M, O'Sullivan M. Intravenous pamidronate treatment of polyostotic fibrous dysplasia associated with the McCune Albright syndrome. Journal of Pediatrics 2000; 137( 3): 403-9.
May 16-19, 2012 in Denver, CO
