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Fibrous Dysplasia



Introduction

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 brittle.

Mild cases of fibrous dysplasia usually cause no signs or symptoms. More serious cases may result in bone pain and deformity, which usually develop before age 15.

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

Signs And 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 may develop during childhood, adolescence or adulthood. 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.
In rare cases, fibrous dysplasia may be associated with abnormalities in the hormone-producing glands of your endocrine system — such as your pituitary gland — that regulate various functions throughout your body. McCune-Albright syndrome, for example, may cause fibrous dysplasia, as well as the following:
  • Very early puberty (precocious puberty). Girls with McCune-Albright syndrome may experience menstrual bleeding and other signs of puberty before age 8. Boys with the condition may show signs of puberty at a younger age than normal, but early puberty in boys is less common than it is in girls.
  • Thyroid gland problems. This small gland in the neck, which affects metabolism, may be enlarged or have cysts.
  • Skin discoloration. Patches of darker skin, known as cafe-au-lait spots, appear light coffee colored on fairer children, but may be difficult to see on children with darker skin.
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 (osteoclastic) tear down (resorb) bone, while other cells (osteoblastic) rebuild it. Fibrous dysplasia disrupts the process, causing old bone to break down faster and replacing normal bone tissue with softer, fibrous tissue.

Treatment

If 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. Some bisphosphonates aren't available as oral medications, and you must receive them through a vein (intravenously). The drug tends to work faster when you receive it through a vein than if you take it orally, and intravenous administration provides an option when you can't tolerate or otherwise aren't a candidate for oral bisphosphonates. 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.
  • 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 from another part of your body. 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.


Information obtained from National Institute of Health
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