Index
It is a disorder where the bone and marrow are replaced with fibrous tissue, resulting in the formation of a weak bone and prone to expansion.
As a result, most complications result from a fracture, deformity, functional deterioration, and pain.
The disease occurs along a broad clinical spectrum ranging from asymptomatic incidental lesions to a seriously disabling condition.
The disease can affect a bone (monostotic) or multiple (polyostotic) and can occur in isolation or with skin macules and hyperfunctioning endocrinopathies, called McCune-Albright syndrome.
More rarely, fibrous dysplasia may be associated with intramuscular myxomas, called Mazabraud syndrome. Fibrous dysplasia is very rare, and a cure is not known. Fibrous dysplasia is not a form of cancer.
Presentation
Fibrous dysplasia is a mosaic disease involving any part or combination of the craniofacial, axillary, and appendicular skeleton.
Therefore, the type and severity of complications depend on the location and extent of the affected skeleton.
The clinical spectrum is vast and ranges from an isolated and asymptomatic monostotic lesion discovered incidentally to a severely disabling disease that practically affects the entire skeleton and leads to vision loss, hearing, and mobility.
Individual bone lesions usually manifest during the first years of life and expand during childhood.
Most clinically significant bone lesions are detectable at ten years, with few new and almost nil clinically significant bone lesions appearing after 15 years.
The total body scan is helpful to identify and determine the extent of bone lesions and should be performed in all patients with suspected fibrous dysplasia.
symptom
Children with fibrous dysplasia typically present with lameness, pain, and pathological fractures in the appendicular skeleton. Frequent fractures and progressive deformities can cause difficulties with mobility and reduced mobility.
In the craniofacial skeleton, fibrous dysplasia may present as a “lump” or painless facial asymmetry. The expansion of craniofacial injuries can lead to progressive facial deformity.
In rare cases, patients may develop vision and hearing loss due to the involvement of optic nerves and auditory ducts, which is more common in patients with excess growth hormone associated with McCune-Albright syndrome.
Fibrous dysplasia usually affects the spine and can cause scoliosis, which can rarely be serious. The untreated progressive scoliosis is one of the few features of fibrous dysplasia, which can lead to early death.
Bone pain is a common complication of fibrous dysplasia. It can occur at any age, but it often develops during adolescence and progresses to adulthood.
Stromal cells of the bone marrow in fibrous dysplasia produce excess amounts of the fibroblast growth factor of the phosphate-regulating hormone-23 (FGF23), which leads to the loss of phosphate in the urine.
Patients with hypophosphatemia may develop rickets/osteomalacia, increased fractures, and bone pain.
Causes
Fibrous dysplasia is a mosaic disease resulting from post-zygotic activation mutations of the GNAS locus protein at 20q13.2-q13.3, which encodes the α subunit of the Gs protein receptor coupled to G.
In bone, the constitutive signaling of Gsα results in damaged differentiation and proliferation of stromal cells of the bone marrow. The addition of these cells causes the replacement of normal bone and marrow with fibrous tissue.
Bone trabeculae are abnormally thin and irregular and often resemble Chinese characters (bone spicules in the biopsy).
Fibrous dysplasia is not hereditary, and there has never been a case of transmission from parents to children.
Diagnosis
X-rays: can be used to determine how extensively your bones are affected.
X-ray: This test uses radioactive markers injected into the bloodstream. The damaged parts of your bones occupy more of the tracers, which appear brighter in the scan.
Biopsy: This test uses a hollow needle to remove a small portion of the affected bone for analysis in the laboratory.
Treatment
The treatment of fibrous dysplasia is mainly palliative and focuses on managing fractures and preventing deformity.
There are no drugs capable of altering the course of the disease. Intravenous bisphosphonates may help treat bone pain, but there is no clear evidence that they strengthen bone lesions or prevent fractures.
Surgical techniques effective in other disorders, such as bone grafting, curettage, and plates and screws, are often ineffective in fibrous dysplasia and should be avoided.
The intramedullary rods are generally preferred to treat fractures and deformities in the lower extremities. Progressive scoliosis can usually be treated with standard instrumentation and fusion techniques.
Surgical treatment in the craniofacial skeleton is complicated by the new growth of postoperative fibrous dysplasia and should focus on correcting functional deformities.
Prophylactic decompression of the optic nerve increases the risk of vision loss and is contraindicated.
The management of endocrinopathies is a critical component of treatment in fibrous dysplasia. All patients with fibrous dysplasia should be evaluated and treated for endocrine diseases associated with McCune-Albright syndrome.
