Fibrous dysplasia for radiologists: beyond ground glass bone matrix

Abstract

Fibrous dysplasia (FD) is a congenital disorder arising from sporadic mutation of the α-subunit of the Gs stimulatory protein. Osseous changes are characterised by the replacement and distortion of normal bone with poorly organised, structurally unsound, fibrous tissue. The disease process may be localised to a single or multiple bones. In McCune-Albright syndrome (MAS), fibrous dysplasia is associated with hyperfunction of endocrine organs and overproduction of melanin in the skin, while Mazabraud syndrome FD is associated with intramuscular myxomas. In radiology, FD is very often automatically associated with the term “ground glass matrix”. However, FD is a complex disease, and knowledge of its unique pathogenesis and course are crucial to understanding imaging findings and potential complications. This article aims to not only summarise the spectrum of radiological findings of osseous and extra-osseous abnormalities associated with FD but also to highlight the pathological base of the disease evolution, corresponding imaging changes and complications based on the disease distribution. We also have provided current recommendations for clinical management and follow-up of patients with FD.Teaching Points• FD is often a part of complex disease, involving not only bone but also multiple other organs.• FD lesions are characterised by age-related histological, radiographical and clinical transformations.• Radiologists play a crucial role in the identification of osseous complications associated with FD.• The craniofacial form of the disease is the most common type of FD and the most difficult form to manage.• Patients with McCune-Albright syndrome may have different extra-skeletal abnormalities, which often require follow-up.

Anterior Bowing of Tibia in an Adult: A Case Report

“…Although typically having a ground-glass appearance, it can also be completely lytic or sclerotic. 4 Characteristic histologic findings indicative of fibrous dysplasia include fibrous stroma consisting of myxofibrous tissue and woven bone.…”

Fibrous Dysplasia, Paget's Disease of Bone, and Other Uncommon Sclerotic Bone Lesions of the Craniofacial Bones

“…The most commonly affected facial bone is the zygomaticomaxillary complex and the sphenoid bone. 8 Mandibular involvement is rare (online ►Fig. S1).…”

“…9 Vision loss due to orbital involvement is only reported in 5%. 8 Development of aneurysmal bone cysts in FD foci is possible and may contribute to rapid progressive symptoms due to compression on adjacent structures. Malignant transformation to osteosarcoma, chondrosarcoma, fibrosarcoma, or fibrohistiocytic sarcoma (formerly known as malignant fibrous histiocytoma) is reported to occur in 2.5%.…”

“…11 Change of imaging appearance throughout follow-up was documented, but spontaneous resolution was not. 8 The involved craniofacial bone usually shows expansion. The mixed pattern of FD can exhibit similar findings to Paget's disease (PD) of bone, hence it is also termed the pagetoid subtype and may cause a diagnostic dilemma.…”

FGF23, Hypophosphatemia, and Emerging Treatments

“…Typical radiograph features include a characteristic "ground glass" appearance. (63) The development of elevated FGF23 and of associated hypophosphatemia correlates with the skeletal burden of FD. (64) Patients with hypophosphatemia are managed with active vitamin D and phosphate similar to other FGF23mediated hypophosphatemia.…”