[Craniofacial fibrous dysplasia]

Fibrous dysplasia of bone is a benign, uncommon, sporadic, congenital skeletal disorder resulting in deformity. This disease arises from activating somatic mutation in GNAS which encodes the α subunit of the G stimulatory protein associated with proliferation of undifferentiated osteogenic cells resulting in marrow fibrosis, abnormal matrix production, and stimulation of osteoclastic resorption upon overproduction of IL-6 observed in dysplastic cells. Fibrous dysplasia may be monostotic or polyostotic. This mutation affecting many tissues, café au lait skin macules and endocrinopathies (precocious puberty, hyperthyroidism, growth hormone excess, Cushing syndrome) may be associated in McCune-Albright syndrome, but also myxoma in Mazabraud syndrome or phosphate diabetes. Diagnosis of craniofacial fibrous dysplasia should be considered in the presence of headache, neuralgia, sensory disorders (vision, hearing, balance, smelling), functional disorders (nasal obstruction, nasolacrimal duct obstruction, non-matching occlusion), infectious complications (sinusitis, otitis, mastoiditis). Such symptoms should lead to perform craniofacial CT scan completed with MRI. Bone biopsy is not systematic. Surgical treatment is discussed in cases of nervous complication, facial deformity or active lesions. In case of pain resistant to conventional analgesics, intravenous bisphosphonates can be proposed. In non-responder patients, several case reports suggest the efficacy of a monoclonal antibody directed against the IL-6 receptor which requires to be confirmed by randomized studies.