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Fibrous Dysplasia —

Mutation of Gene GNAS1 leading to inhibition of differentiation and proliferation of bone stromal cells leading to replacement of bone by fibrous tissue and immature woven bone.

Location — Metaphyseal lesion extending into Diaphysis

Age group — 5-30 years

MC site (overall ) – Proximal femur

MC site in craniofacial area – zygomatic maxillary complex

Types :

Monostotic – Single bone involvement ( six times more common ) ( usually doesn’t progress )

Polyostotic – Multiple bone involvement ( progresses )

Clinical Presentation : Pain , Deformity and Pathological fracture

Generalised fibrous Dysplasia involving skull and face is called Leontiasis Ossea

X-ray – Multiloculated , translucent lesion expanding the cortex of the bone ( Ground Glass appearance )

In certain cases , surrounded by sclerotic rim called RIND Sign.

In neglected cases of the proximal femur , medial wall collapses leading to Shepherd Crook Deformity.

Biopsy – Chinese letter pattern Treatment

 

Excisional curettage plus Bone Grafting.

MC non skeletal manifestation of FD – Cafe au lait spots