Diseases & Conditions

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.

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 basic cause of fibrous dysplasia is unknown. There's no cure for fibrous dysplasia. Treatment focuses on relieving 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, including:

• 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.

When to see a doctor
See your doctor if you or your child develops bone pain, has difficulty walking or fractures a bone, particularly more than once.

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.

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 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. Surgically removing a sample of affected bone for examination under a microscope is necessary only if your doctor suspects cancer. During a biopsy, a surgeon removes a small piece of your affected bone for analysis in a laboratory.

A biopsy can be performed as an open biopsy, meaning that it requires anesthesia and surgery to get to your bone. In some situations, a surgeon inserts a long needle through your skin into your bone to take a biopsy (fine-needle aspiration). This procedure requires local anesthetics to numb the area where the needle is inserted.

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.

Bisphosphonates
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 grafted from another part of your body or from donated cadaver bone tissue. 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.