Fibrous dysplasia is a rare, non-cancerous bone disorder where normal bone tissue is replaced by abnormal fibrous tissue. This replacement can weaken the bone, potentially leading to fractures or deformities.
Defining Fibrous Dysplasia
Fibrous dysplasia results from a spontaneous genetic mutation in the GNAS gene, which is not inherited from parents. This mutation affects cells responsible for bone formation, leading to disorganized, fibrous bone that lacks the strength of healthy bone, making affected bones more fragile and susceptible to bowing or breaking.
The condition primarily presents in two forms. Monostotic fibrous dysplasia involves only a single bone and is the most common type. Polyostotic fibrous dysplasia affects multiple bones, often on one side of the body, and is generally more severe. A more extensive form of polyostotic fibrous dysplasia is McCune-Albright syndrome, which includes bone involvement along with other features like skin pigmentation and hormonal abnormalities.
Recognizing the Manifestations
The signs and symptoms of fibrous dysplasia can vary significantly depending on the location and extent of the affected bone(s). Bone pain is a common symptom, often described as a dull ache, and can intensify with activity or stress on the bone. Swelling, limping, and bone deformities, such as bowing of long bones or facial asymmetry, are also frequently observed.
Fractures, especially in weight-bearing bones, can be an early indicator due to the weakened bone structure. Fibrous dysplasia can affect any bone, but it is most often found in long bones like the femur (thighbone) and tibia (shinbone), as well as the ribs, skull, and facial bones. When the skull and facial bones are involved, it can lead to issues like jaw misalignment, nasal congestion, or problems with vision or hearing due to nerve compression.
Navigating Diagnosis and Management
Diagnosing fibrous dysplasia begins with a physical examination and a detailed patient history, especially noting any pain, swelling, or deformities. Imaging studies are important for identifying and characterizing the bone lesions. X-rays may reveal areas of abnormal bone with a characteristic “ground-glass” appearance, indicating the fibrous tissue replacing normal bone.
Computed tomography (CT) scans offer more detailed cross-sectional images, particularly useful for evaluating craniofacial involvement, while magnetic resonance imaging (MRI) can assess the extent of the lesion and surrounding soft tissues. A bone scan can help identify all affected bones throughout the skeleton. A definitive diagnosis often requires a bone biopsy, involving microscopic examination of a tissue sample from the affected area to confirm the presence of fibrous tissue.
Management of fibrous dysplasia focuses on alleviating pain, preventing fractures, and correcting any deformities. Medical treatments may include bisphosphonates, which can help reduce bone pain and strengthen the bone, thereby lowering the risk of fractures. These medications work by slowing down bone breakdown.
Surgical interventions are often necessary, especially for symptomatic lesions, fractures, or progressive deformities. Procedures can involve curettage, where the abnormal fibrous tissue is scraped out of the bone, sometimes followed by bone grafting to fill the cavity and stabilize the bone. Internal fixation, using metal rods, plates, or screws, may be used to support weakened bones, prevent fractures, or correct existing deformities. For craniofacial involvement, surgery may aim to restore facial symmetry, decompress nerves, or improve function.
Outlook and Support
The progression of fibrous dysplasia can vary significantly among individuals. In many cases, the condition tends to stabilize after skeletal maturity, with lesions stabilizing once bone growth ceases. However, the abnormal bone does not disappear, and symptoms can persist into adulthood.
While generally non-cancerous, a very rare complication is the malignant transformation of fibrous dysplasia into cancerous tumors, occurring in less than 1% of patients, primarily in severe polyostotic forms. Patients with extensive involvement, especially in the skull and face, might experience nerve compression, potentially leading to vision or hearing changes. A multidisciplinary team, including orthopedic surgeons, endocrinologists, geneticists, and pain specialists, is often involved in providing comprehensive care. Patient education and participation in support groups can be beneficial for managing symptoms and maintaining quality of life.