Oral Pathology Short Case 5 - 15-year old Female - Lesion present in anterior maxilla. A mixed radiodense lesion

 Answer : Fibrous dysplasia

Skeletal anomaly which normal bone is replaced and distorted by poorly organized and inadequately mineralized immature bone and fibrous tissue

Single bone – Monostotic (Craniofacial fibrous dysplasia – monostotic variant)

Multiple bone – Polyostotic fibrous dysplasia

Multiple bone + multiple endocrine abnormalities – Mc cune Albrights syndrome 

7 % of all benign tumours

Disorder of growing bone in children and adolescents

A missense mutation in GNAS gene – overexpression of cAMP – changes in properties of osteoprogenitor cells

Milder forms affect few bones – craniofacial and femur 

Maxilla > mandible

Clinical – 

Painless swelling of jawbones, Facial asymmetry

First 2 decades of life

Displacement of teeth, malocclusion 

Paranasal sinuses, orbits and foramina of the base of the skull can produce – Visual loss, hearing loss, headache, nasal obstruction

Radiology – Classic lesions show ground glass appearance 

Table 4 Histopathology

Fibrous	Osseous
Varying proportions
Fibroblastic cells  Mitosis is rare	Irregularly shaped trabaculae Immature woven bone No osteoblastic rimming Chinese character appearance  May undergo progressive maturation and lamella bone

Table 5 GNAS gene mutation stage and disorders

Early embryonic- Pluripotent stem cell	In multiple cell types, including osteoblasts, melanocytes, and endocrine cells	Jaffe-Lichtenstein syndrome, characterized by polyostotic fibrous dysplasia and café au lait (coffee with milk) pigmentation McCune-Albright syndrome, characterized by polyostotic fibrous dysplasia, café au lait pigmentation, and multiple endocrinopathies Mazabraud syndrome, characterized by fibrous dysplasia and intramuscular myxomas
Late embryonic - Skeletal progenitor	Only osteoblasts will be affected	Polyostotic fibrous dysplasia
Postnatal life - osteoblasts	Single bone will be affected	Monostotic fibrous dysplasia

Treatment depends on the functional and aesthetic abnormality

In most case lesions tend to stabilize with skeletal maturity

Simple contouring 

Rarely malignant transformation

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