Fibrous dysplasia is benign developmental anamoly of mesenchymal precursor of bone with progressive replacement of normal bone marrow by immature fibrous-osseous tissue.

In craniofacial fibrous dysplasia  there is unilateral overgrowth of facial bones and calvarium with extended diploid space and outward expansion of outer table.

Differential diagnosis include; juvenile ossifying fibroma, cherubism , renal osteodystrophy.