The clinical spectrum is very broad, ranging from an isolated, asymptomatic monostotic lesion discovered incidentally, to severe disabling disease involving practically the entire skeleton and leading to loss of vision, hearing, and/or mobility.

[8] Total body scintigraphy is useful to identify and determine the extent of bone lesions, and should be performed in all patients with suspected fibrous dysplasia.

Bone marrow stromal cells in fibrous dysplasia produce excess amounts of the phosphate-regulating hormone fibroblast growth factor-23 (FGF23), leading to loss of phosphate in the urine.

[12] Fibrous dysplasia is a mosaic disease resulting from post-zygotic activating mutations of the GNAS locus at 20q13.2-q13.3, which codes for the α subunit of the Gs G protein-coupled receptor.

Computerized tomography (CT) or magnetic resonance imaging (MRI) scans may be used to determine how extensively bones are affected.

CT can better demonstrate the typical "ground glass" appearance, which is a highly specific radiological finding, while MRI can show cystic areas with fluid contents.

A biopsy, which uses a hollow needle to remove a small piece of the affected bone for laboratory analysis, can diagnose fibrous dysplasia definitely.

[20] Surgical management in the craniofacial skeleton is complicated by frequent post-operative FD regrowth, and should focus on correction of functional deformities.

In particular untreated growth hormone excess may worsen craniofacial fibrous dysplasia and increase the risk of blindness.