What is fibrous dysplasia (FD)?

Fibrous dysplasia (FD) is an uncommon disorder of the skeleton that is rarely cancerous (less than 1 percent). This disorder results in fibrous bone-like tissue that replaces normal, healthy bone, causing the affected areas to be more susceptible to fractures (broken bone).

FD can affect one bone (known as monostotic FD), multiple bones (known as polyostotic FD) or the entire skeleton (known as panostotic FD). It may also be associated with darkened patches of the skin known as café au lait macules. Most often, it affects the bones of the legs, upper arms, skull (including the facial bones) and ribs.

Who is likely to have fibrous dysplasia (FD)?

Anyone can have fibrous dysplasia, and it can be diagnosed at any age. The condition is not linked to any one ethnicity or geographical location, and affects males and females equally. It is believed that the bone abnormality occurs in childhood, but may go unnoticed unless there is associated pain, a limp develops or a fracture occurs.

How common is fibrous dysplasia (FD)?

Fibrous dysplasia is rare. And because mild cases may go undiagnosed, it is difficult to define the true frequency of this disorder.

What causes fibrous dysplasia (FD)?

Fibrous dysplasia results from a genetic mutation (change) on chromosome 20. This mutation happens on one gene that directs bone formation and growth, but what causes this mutation to occur remains unknown.

What are the symptoms of fibrous dysplasia (FD)?

The symptoms of fibrous dysplasia vary greatly depending on:

  • How many bones are affected
  • Location in the body of the affected bones
  • Whether any injuries, like fractures, have occurred

People living with fibrous dysplasia may have no signs or symptoms at all, but for others living with FD signs and symptoms may include:

  • Fatigue, particularly in young children
  • Pain and weakness in the areas affected
  • Fractures or breaks
  • Misshapen bones (bone deformity)
  • Cafe au lait spots
  • Signs and symptoms of underlying endocrine disorders such as growth hormone excess, overactive thyroid and early puberty

Because FD can affect any bone in the body, symptoms may range from mild to severe. Some symptoms may seem unrelated to the bones, such as:

  • Nasal congestion, uneven jaws or bulging eyes if bones in the face are affected
  • Vision loss or hearing impairment if specific nerves become compressed due to the fibrous bone tissue

In rare cases, fibrous dysplasia occurs as part of a group of conditions known as McCune-Albright syndrome. This syndrome affects the bones, endocrine (hormone-producing) tissues and skin.

Last reviewed by a Cleveland Clinic medical professional on 08/06/2018.

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