Fibrous dysplasia

Source:  Fibrous dysplasia    Tag:  what is fibrous dysplasia

Fibrous dysplasia is a bone disorder in which scar-like (fibrous) tissue develops in place of normal bone. As the bone grows, the softer, fibrous tissue expands, weakening the bone. Fibrous dysplasia can cause the affected bone to deform and become susceptible to fracture.

Most people with fibrous dysplasia are diagnosed during adolescence or early adulthood. Mild cases usually cause no signs or symptoms. More-serious cases of fibrous dysplasia may result in bone pain and deformity.

The basic cause of fibrous dysplasia is unknown. There's no cure for fibrous dysplasia. Treatment focuses on relieving signs and symptoms.

Symptoms:

Fibrous dysplasia can affect any bone in your body. Most people with the disorder have only one affected bone — a form called monostotic fibrous dysplasia — and develop no signs or symptoms. When the condition affects more than one bone, it's known as polyostotic fibrous dysplasia. Bones most commonly affected are:


  • Thighbone (femur)
  • Shinbone (tibia)
  • Pelvic bones
  • Ribs
  • Skull
  • Facial bones
  • Upper arm bone (humerus)


Fibrous dysplasia may cause few or no signs and symptoms, particularly if the condition is mild. Signs and symptoms typically develop during the teens or 20s. If you have the polyostotic form, you're more likely to develop signs and symptoms, usually by age 10. More severe fibrous dysplasia may cause:


  • Bone pain
  • Difficulty walking
  • Bone deformities
  • Fractures


Causes:

You develop fibrous dysplasia before birth, and its development has been linked with a gene mutation that affects the cells that produce bone. No one knows what causes the mutation, but it isn't inherited from your parents, and you can't pass it on to your children.

Bones are living tissue, so even after you stop growing, your bones are in a continuous process of renewal known as remodeling. In the process, certain bone cells (osteoclasts) tear down (resorb) bone, while other cells (osteoblasts) rebuild bone. Fibrous dysplasia disrupts the process, causing old bone to break down faster and replacing normal bone tissue with softer, fibrous tissue.

Complications:

Besides bone fractures, severe fibrous dysplasia can lead to:

Bone deformity. The weakened area of an affected bone can cause the bone to bend (bow). If your spine is affected, you can develop scoliosis, an abnormal curving of the spine.
Vision and hearing loss. The nerves to your eyes and ears may be surrounded by affected bone. Severe deformity of facial bones can lead to loss of vision and hearing, but it's a rare complication.
Arthritis. If leg and pelvic bones are deformed, arthritis may form in the joints of those bones.
Cancer. Rarely, an affected area of bone can become cancerous. This rare complication usually only affects people who have had prior radiation therapy.

Tests and diagnosis:

If you have monostotic fibrous dysplasia, you may not know it until it's discovered incidentally on an X-ray for another condition. If you have signs and symptoms, your doctor will perform a physical examination and order X-rays of the affected bones. On X-ray, fibrous dysplasia appears as an abnormal section of bone (lesion) that has the hazy appearance of ground glass.

In some cases, your doctor may order more tests to confirm the diagnosis or to determine the extent of the disorder. They include:

Imaging tests. Computerized tomography (CT) or magnetic resonance imaging (MRI) scans may be used to determine how extensively your bones are affected.
Bone scan. This test uses radioactive tracers, which are injected into your body. Your bones take up the tracers and emit radiation that's captured by a special camera, which produces a picture of your skeleton. Your doctor may order a bone scan to determine whether your fibrous dysplasia is monostotic or polyostotic.
Bone biopsy. This test uses a hollow needle to remove a small piece of the affected bone for laboratory analysis. You'll receive local anesthetics to numb the area where the needle is inserted. In rare instances, an open biopsy — requiring general anesthesia and a surgical incision — may be necessary.

Treatments and drugs:

f you have mild fibrous dysplasia that's discovered incidentally and you have no signs or symptoms, your risk of developing deformity or fracturing your bone is low. Your doctor can monitor your condition with follow-up X-rays every six months. If there's no progression, you don't need treatment.

If you develop signs and symptoms, treatment may include medications or surgery.

Medications
Medications called bisphosphonates, including pamidronate (Aredia) and alendronate (Fosamax), are used to inhibit bone breakdown, preserve bone mass and even increase bone density in your spine and hip, reducing the risk of fractures. Doctors use these medications primarily for adults to treat osteoporosis and increase bone density, but bisphosphonates may also reduce bone pain associated with fibrous dysplasia and, in some cases, improve bone formation.

Little is known about the use of bisphosphonates for children and adolescents, but some studies indicate they may help relieve pain in children and adolescents with severe fibrous dysplasia.

Oral bisphosphonates are generally well tolerated, but may irritate your gastrointestinal tract. If you can't tolerate oral bisphosphonates or if your doctor recommends a drug that's not available in oral form, you may receive bisphosphonates through a vein (intravenously). You can't take bisphosphonates if you have serious kidney disease or low blood-calcium levels.

Surgery
Your doctor may recommend surgery in order to:


  • Correct a deformity
  • Correct a difference in limb lengths
  • Fix a fracture
  • Remove an affected area of bone (lesion) that's causing you difficulty
  • Relieve pressure on a nerve, particularly if the lesion is in your skull or face


Surgery may involve removing the bone lesion and replacing it with bone grafted from another part of your body or from bone tissue donated from a deceased donor. Your surgeon may insert metal plates, rods or screws to stabilize the bone and the graft. Risks include infection, blood clots and bleeding. In addition, a bone graft may not last.