Presented by Int. 吳建霆 Dec. 27th, 2005 Fibrous dysplasia Presented by Int. 吳建霆 Dec. 27th, 2005

12 years-old boy

12 years-old boy

12 years-old boy

Introduction FD is a developmental dysplastic disorder of bone in which immature woven bone is formed directly from abnormal fibrous connective tissue Disorganized, immature bone surrounded by primitive fibrous tissue cannot mature into normal lamellar bone in affected areas It is characterized by expanding fibroosseous tissue within affected bones and is a lesion of the growing skeleton FD of bone is a rare congenital disease characterized by a focal proliferation of fibrous tissue in the bone marrow, leading to osteolytic lesions, deformities and fractures

Introduction Monostotic FD affects only one bone, most commonly the ribs, proximal femur, and craniofacial bones Polyostotic FD affects many bones, up to 75% of the skeleton Monostotic FD is 7-10 times more common than polyostotic FD Monostotic FD often becomes inactive after puberty. It may reactivate during pregnancy Polyostotic FD typically remains active throughout life

Epidemiology The true incidence is unknown It may account for about 2.5% of bone disorders and 7%~10% of so-called benign bone tumors Males are affected more often than females, except in McCune-Albright syndrome

Pathophysiology in osteoprogenitor cells cAMP-dependent protein kinase product of c-fos Fos binding with Jun to form a heterodimer beta-chain of platelet-derived-growth-factor

Clinical symptoms Many patients with FD are asymptomatic The first symptoms often present during childhood or adolescence, with a median onset age of 8 years Pain Seldom of articular origin The consequence of an incomplete fracture The intensity of the pain is variable Pseudo-inflmmatory characteristics

Clinical symptoms Bone deformities Fractures Shepherd's crook deformity of the tibia or femur Facial asymmetry and swelling Exophtalmy, abnormalities of tooth development and leontiasis ossea Fractures Pathological fracture Deformities altering the mechanical properties of long bones during growth Osteolytic lesions, which reduce cortical thickness

Shepherd's crook deformity

McCune-Albright syndrome MAS was first described as a triad defined by Precocious puberty Polyostotic FD Areas of brown hyperpigmentation of the skin (cafe�-au-lait spots) Multiple endocrine abnormalities may co-exist Thyroid nodules and hyperthyroidism Adrenal hyperplasia and hypercortisolism Pituitary tumors with acromegaly or hyperprolactinaemia Hypophosphataemic rickets and osteomalacia resulting from an inappropriately decreased reabsorption of phosphate from the renal tubules

McCune-Albright syndrome Non-endocrine abnormalities are occasionally present Liver, heart, thymus, spleen, liver, bone marrow, gastrointestinal tract and brain

Craniofacial form This pattern of the disease occurs in 10-25% of patients with the monostotic form and in 50% with the polyostotic form It also occurs in an isolated craniofacial form Sites of involvement most commonly Frontal, sphenoid, maxillary, and ethmoidal bones The occipital and temporal bones are less commonly affected

Craniofacial form Orbital and periorbital bones involvement Hypertelorism, cranial asymmetry, facial deformity, visual impairment, exophthalmos, and blindness Sphenoid wing and temporal bones involvement Vestibular dysfunction, tinnitus, and hearing loss Cribriform plate involvement Hyposmia or anosmia Maxillary and mandibular involvement Displacement of the teeth and distortion of the nasal cavities

Radiological features The radiological characteristics depend on the degree of ossification of FD lesions The typical lesions appear to expand from the medulla to the cortex and are cystic These lesions generally thin the surrounding cortical bone The cortex sometimes becomes sclerotic The lesions usually exhibit a ground glass appearance or are radiolucent Calcification may be visible

Fibrous dysplasia

Radiological features CT scan Confirms a lesion that is confined to the interior of the bone with no soft tissue component Helpful in distinguishing fibrous dysplasia from a malignancy Features include osteolysis, destruction of sclerotic margins, and cortical destruction with soft tissue extension Depict a homogeneous matrix MRI Intermediate signal intensity on T1-weighted images High signal intensity on T2-weighted images

Fibrous dysplasia T1 T2

Histology The most prominent histological characteristic is fibrous tissue made up of immature mesenchymal cells, expanding from the medullary cavity to the cortical bone Long, spindle-shaped fibroblast-like cells are arranged in parallel arrays or whirls They are embedded in a matrix of parallel collagen fibrils Spicules of woven bone are located in the fibrous tissue Islands of hyaline cartilage can sometimes be noted embedded in the fibrous tissue

Fibrous dysplasia Chinese letters

Diagnosis The diagnosis should be based on the clinical, radiological and pathological findings In polyostotic FD or in MAS, the radiological findings are often sufficient to provide a high probability of the diagnosis, and a bone biopsy is generally unnecessary In contrast, many diagnoses are possible in monostotic FD, and a bone biopsy may be useful to confirm both the diagnosis of FD and that the lesion is not malignant

Differential diagnoses The most common differential diagnoses are Paget's disease of bone, meningioma, angioma and osteofibrous dysplasia

Treatment Medical therapy Treatment is usually conservative and primarily to prevent deformity In upper extremity lesions, more than 80% respond to nonsurgical management No specific medical treatment exists for the bone disease, although early evidence suggests that vitamin D and bisphosphonates may be helpful in ameliorating pain and possibly in reconstituting lesions with normal bone

Treatment Surgical therapy Indications Severe or progressive disease Nonunion Persistent pain Fracture of a weight-bearing bone Curettage, cortical bone grafting, internal fixation of long bones Cancellous bone grafts are not recommended Preventative surgical measures are necessary when the risk of fracture is very high So far, the only treatment for FD has been orthopaedic surgery, consisting of preventive measures (curettage, bone grafting and the internal fixation of long bones) and the management of fractures

Prognosis The general prognosis in FD is often good Polyostotic forms seem to be more aggressive The recurrence rate has been reported at 21% following curettage and grafting but probably is closer to 100% if patients are monitored for many years The prognosis also depends on the occurrence of complications

Complications Malignancies are rare in FD, their frequency varying from 0.5 to 4% Risk factors include Polyostotic form Past radiation therapy Facial bone involvement McCune-Albright syndrome The most common malignancy seen is osteosarcoma, followed by fibrosarcoma and chondrosarcoma

Complications The early recognition of a sarcoma in FD Rapidly developing symptoms such as pain and swelling The characteristic finding on X-ray is the extension of the lesion through the cortex in soft tissues Neurological complications occur as a result of nerve compression from the expansion of FD lesions Exceptional consequences are blindness, deafness and spinal cord compression