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| REVIEW ARTICLE |
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| Year : 2016 | Volume
: 28
| Issue : 4 | Page : 403-408 |
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Craniofacial fibrous dysplasia: A summary of findings with radiological emphasis
Ashwini Deshpande1, Giridhar S Naidu2, Balaji Gandhi Babu Dara3, Manas Gupta4
1 Department of Oral Medicine and Radiology, People's Dental Academy, Bhopal, Madhya Pradesh, India
2 Department of Oral Medicine and Radiology, New Horizon Dental College and Research Institute, Bilaspur, Chhattisgarh, India
3 Department of Oral Medicine and Radiology, Panineeya Mahavidyalaya Institute of Dental Sciences and Research Centre, Hyderabad, Telangana, India
4 Department of Oral Medicine and Radiology, Rishiraj College of Dental Sciences and Research Center, Bhopal, Madhya Pradesh, India
| Date of Submission | 04-Nov-2015 |
| Date of Acceptance | 21-Dec-2016 |
| Date of Web Publication | 21-Feb-2017 |
Correspondence Address:
Dr. Ashwini Deshpande
H-3/2, B.D.A. Colony, Nayapura, Lal Ghati, Airport Road, Bhopal - 462 031, Madhya Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0972-1363.200631
 Abstract | | |
Fibrous dysplasia is a benign bone disorder where normal bone gets replaced by fibrous connective tissue. Although histopathology is a gold standard in the diagnosis of any pathology, radiology remains an important investigation. This is attributed to the fact that it not only helps in the diagnosis and treatment planning but also is an indispensible tool for follow up of such patients. Keywords: Bone, craniofacial fibrous dysplasia, fibroosseous lesion, fibrous dysplasia, maxillofacial
How to cite this article:
Deshpande A, Naidu GS, Dara BG, Gupta M. Craniofacial fibrous dysplasia: A summary of findings with radiological emphasis. J Indian Acad Oral Med Radiol 2016;28:403-8 |
How to cite this URL:
Deshpande A, Naidu GS, Dara BG, Gupta M. Craniofacial fibrous dysplasia: A summary of findings with radiological emphasis. J Indian Acad Oral Med Radiol [serial online] 2016 [cited 2021 Jan 28];28:403-8. Available from: https://www.jiaomr.in/text.asp?2016/28/4/403/200631 |
| Introduction | |  |
Fibroosseous lesions are a diverse group of processes that are characterized by replacement of normal bone by fibrous tissue containing a newly formed mineralized product. Whereas fibrous dysplasia (FD), a type of fibroosseous lesion, is a developmental tumor-like condition where normal bone is replaced by an excessive proliferation of cellular fibrous connective tissue intermixed with irregular bony trabeculae.[1] The ability to form mature normal lamellar bone is defective, resulting in a development arrest at the level of mature bone. The abnormal trabeculae of woven bone form a disordered whorled pattern and the bone undergoes active but disordered osteoblastic activity.[2] It represents approximately 7% of all benign osseous tumors and may affect any bone of the skeleton.[3]It is thought to be a genetic sporadic disease of the bone that may affect single or multiple bones (monostotic, polyostotic). FD occurring in multiple adjacent craniofacial bones is regarded as monostotic (craniofacial FD).[4] Preosteoblasts undergo excessive proliferation and differentiation, which occur due to a mutation in the guanine nucleotide-binding protein (GNAS1), gene which encodes for an α-subunit of a signal transducing G-protein (Gs-α).[5],[6] This mutation causes a continuous activation of the G-protein, which causes an upregulation in the production of cAMP, which results in increased endocrine activity. In addition to this, the upregulation also causes a proliferation of the melanocytes, which result in café-au-lait spots. cAMP is thought to also have an effect on osteoblastic differentiation, which results in fibrous dysplasia. GNAS1 is located on chromosome 20q13.2-13.3.[7] FD has for long been considered a benign developmental process. Whether it may possibly be neoplastic has been debated. In the recent past, repeated chromosomal aberrations have been reported suggesting a frank neoplastic process.[6],[8]
| Clinical Features | | |
FD occurring in multiple adjacent craniofacial bones is regarded as monostotic (craniofacial FD).[4] Females are more commonly affected than males, almost twice as much according to some authors; however, the others differ in that males and females are equally affected.[1],[9] The monostotic form is more common and affects people at 20–30 years of age, whereas the polyostotic form has its onset mainly in children younger than 10 years of age. McCune Albrights syndrome is a special form of polyostotic fibrous dysplsia (PFD), with an incidence of only 3% and has an association with other endocrine disorders.[10],[11] The authors review 10 cases diagnosed histopathologically as fibrous dysplasia. The demographic details, site of involvement, associated symptoms, and the radiological appearance is summarized in [Table 1]. | Table 1: Radiological appearances of fibrous dysplasia of craniofacial bones
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It begins as an asymptomatic painless swelling in the affected area leading to facial asymmetry,[1],[4] with the maxilla being more commonly affected than the mandible. With the mandible involved, it may safely be called monoostotic FD, however, when the maxilla is involved, it may be more apt to call it craniofacial FD rather than PFD [Figure 1] and [Figure 2].[1] Occasionally, patients may report with a painful, suppurative swelling with ulceration, which is very atypical of fibrous dysplasia.[9] Depending on the site and bone involvement, other symptoms include nasal obstruction when paranasal sinuses are involved,[12] visual disturbances if the orbit is involved, whereas temporal bone lesions may produce hearing loss. Occasionally, the patient may also complain of facial pain, headaches, or facial numbness.[13],[14],[15] | Figure 1: Coronal computed tomography section showing involvement of the maxilla and zygomatic bone in a patient with fibrous dysplasia
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 | Figure 2: Coronal computed tomography section of the same patient as shown in Figure 1 with involvement of sphenoid bone
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Although serum calcium and phosphorous values may remain unchanged, there may be an increase in serum alkaline phosphatase, which is thought to be unrelated to the extent of disease.[16] In most of our cases, these values remained within normal limits, however, for one case, where there was a significant increase in alkaline phosphatase levels, although this patient had the smallest lesion as compared to the other presented cases.
| Syndrome Association | | |
Multiple bone involvement with café-au-lait pigmentation is suggestive of Jaffe–Lichtenstein syndrome. While PFD associated with café-au-lait pigmentation and endocrinopathies including hyperthyroidism, sexual dysfunction is recognized as McCune Albright syndrome. There have been sporadic reports of other syndrome associated FD. Mazabraud's syndrome is one such syndrome where FD is associated with multiple soft tissue myxomas.[1],[17]
| Imaging | | |
Intraoral radiography and panoramic radiographs are the most commonly used firstline imaging, although computed tomography gives images which are most representative of the lesion. Magnetic resonance imaging (MRI) has been tried but its success depends on the components.
FD, according to the radiological pattern of presentation, may be grossly classified as pagetoid, sclerotic and cyst-like. The pagetoid appearance is the most common, while the sclerotic form, commonly known as the ground glass appearance, and the cyst-like form are thought to be less common and also affect the younger age group. It is believed that the latter two are predecessors of the more common pagetoid variety. The pagetoid alternates between the radiodense and radiolucent areas, sclerotic, which is that of a marked homogenous increase in bone density, is usually associated with bone expansion, and the cyst-like, which are spherical or ovoid radiolucent area surrounded by dense limits.[2],[18] Radiographically, the borders of FD are contiguous with normal adjacent bone.[1],[2] Displacement of teeth with root resorption has been reported but is rare. Internal density and trabecular pattern of FD vary in appearance, with variation more commonly seen in the mandible. A distinctive characteristic feature is a fingerprint appearance caused by organization of abnormal trabeculae into a swirling pattern.[19] Periapically, there may be a narrowing of periodontal ligament (PDL) space and ill-defined lamina dura. The PDL space may appear widened because of the increased density of bone.[1] FD may expand into the antrum by displacing its cortical boundary. The last wall to be involved is the most posterosuperior portion. The shape of the bone expansion of FD into the antrum reflects the original outer contour of the antral wall, which is different from the more convex extension of a neoplasm [Figure 3].[19] FD behaves peculiarly in the mandible because it displaces the inferior alveolar canal superiorly. | Figure 3: Coronal computed tomography section showing maintained antrum morphology
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Some other authors opine that FD varies in its radiographic presentation, with three basic patterns that include a rather small unilocular radiolucency or a larger multilocular radiolucency, both having a well-circumscribed border. The second variant is similar to the first, however, it has increased trabeculation rendering the image mottled. The third variant is the ground glass appearance or peau d'orange which is more opaque than the former and has many delicate trabeculae.[11],[20] Obisesan et al. have classified FD of craniofacial bones into six different types. The radiological type and its description, as seen in our cases, are summarized in [Table 2].[21]
MRI has also been used as an imaging modality with limited success. Largely, a low-to-intermediate signal intensity is seen. Small regions of high signal intensity represent cysts. Cellular regions and areas containing mostly bony trabeculae, otherwise known as the ground glass appearance, appear dark on a T2-weighted image. Cystic lesions tend to appear brighter but do not enhance although the fibrous areas often enhance prominently.[2] MRI may also help in evaluating cranial nerve involvement and soft tissue structures adjacent to the lesion.[2] Bone scintigraphy has been recommended to rule out the polyostotic variant.[3] Most FD lesions affecting the craniofacial skeleton are monostotic, although it is necessary to perform a complete skeletal evaluation to rule out the possibility of a polyostotic variant.[22]
| Differential Diagnosis | | |
Metabolic bone diseases, such as hyperparathyroidism, produce similar patterns, although the pattern is more generalized and does not cause bony expansion. Paget's disease may have a similar appearance, may also cause bony expansion, but involves the whole bone, and is a disorder of the elderly. Differentiation of osteomyelitis is important, presenting as the usual enlargement of jaws; however, reactive bone formation is usually seen at the periosteum in patients with osteomyelitis. Osteosarcoma may have more aggressive radiographic changes including a more bizarre internal structure.[19]
| Histopathological Features | | |
Irregularly-shaped immature bone in a loose fibrous stroma is typically seen. The trabeculae are curvilinear shaped giving a Chinese script pattern. These trabeculae are thought to be metaplastic [Figure 4].[1] Characteristically, bundles of collagen fibres oriented perpendicular to the bone surface, compatible with Sharpey-fibers, can be demonstrated.[16] Unlike other fibroosseous lesions, FD demonstrates a monotonous pattern rather than a haphazard mixture of woven and lamellar bone mixed with spheroid particles. The lesional bone fuses with normal bone at the periphery, such that no capsule or line of demarcation is present.[1] This corelates with radiographic findings where the lesional bone blends imperceptibly into the surrounding normal bone. | Figure 4: Histopathology of fibrous dysplasia showing a Chinese letter arrangement of trabeculae
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 | Figure 5: Maxillary occlusal radiograph showing an orange peel appearance
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 | Figure 7: Intraoral periapical radiograph showing a typical fingerprint appearance
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 | Figure 8: Intraoral periapical radiograph showing gradual merger of pathological bone with normal bone
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 | Figure 10: Extraoral radiograph showing a pagetoid appearance of the mandible
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| Management and Prognosis | | |
There have been reports of medical management of FDs with bisphosphonates; however, the results have not been promising.[15] Some authors claim improvement of pain and inflammatory symptoms, stabilization and reduction of bone destruction, increase of the osseous density, recalcification of osteolytic lesion in 50% of the patients, improvement of the radiologic aspects and osseous metabolism.[3]
Clinical findings of increasing pain and an enlarging soft tissue mass suggest malignant change. Rarely, a sarcoma may develop in patients with FD. Osteosarcoma is the most common type, which most often affects the craniofacial bones. Contrary to popular belief, this development has been noted in tissue, which has not received radiation as a part of the treatment in FD.[23],[24]
Fibroosseous lesions represent a spectrum of diseases, which could sometimes result in severe disfigurement, as seen in some of the above cases. An insight into the genetic basis of this disease process and an understanding of the clinical and radiological features is essential not only for the diagnosis but also in making a sound decision for the control of this disease in its various stages of progression.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]
[Table 1], [Table 2]
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