Osteogenesis imperfecta, also known as brittle bone disease, is a genetic disorder that causes bones to break easily without cause. The condition affects the body's ability to produce collagen, a protein in the body's connective tissue. There are four types of osteogenesis imperfecta, which vary greatly in how severe they are:
- Type I is the most common and mildest form
- Type II is the most severe. It frequently causes death at or near birth. It affects about 10% of all persons with osteogenesis imperfecta.
- Type III causes many bone fractures, including ones that occur before birth. This type affects about 20% of all persons with osteogenesis imperfecta.
- Type IV is between Types I and III in severity.
An estimated 20,000 to 50,000 people in the United States have osteogenesis imperfecta.
The symptoms of osteogenesis imperfecta vary a great deal, even among people with the same type and within the same family. Not all of the signs show up in every case. In general, the symptoms of osteogenesis imperfecta include:
- A tendency toward spinal curvature
- Abnormalities in collagen ranging from the body producing too little to structural problems
- Bones that break easily (most before puberty)
- Brittle teeth
- Changes in the sclera (whites of the eyes), which may have a blue, purple or gray tint
- Height that ranges from shorter than average to normal, depending on the form of the disease
- Loose joints and muscle weakness
- Loss of hearing beginning in the early 20s or 30s
- Triangular face
In more severe forms of osteogenesis imperfecta, there may be bone deformities, poor lung development and lung problems, a barrel-shaped chest, poor muscle development in the arms and legs.
Causes and Risk Factors
Osteogenesis imperfecta is caused by a faulty gene that affects the body's ability to produce collagen. The quantity of collagen produced is either lower or of a poorer quality.
If one parent has osteogenesis imperfecta, a child has a 50% chance of having the condition. Sometimes, however, the disease appears in children who have no family history of osteogenesis imperfecta.
It is often, but not always, possible to diagnose osteogenesis imperfecta on the basis of the symptoms it causes. Biochemical (collagen) or molecular (DNA) tests can help confirm the diagnosis in nearly 90% of all Type I cases. These tests usually take several weeks before results are known.
A negative collagen test doesn't necessarily rule out the possibility of a child having another form of osteogenesis imperfecta or even Type 1 osteogenesis imperfecta that couldn't be detected by the test.
Currently, there isn't a cure for osteogenesis imperfecta. Treatment focuses on: managing the symptoms, preventing complications, preserving independent movement and developing bone mass and muscle strength. This is done by treating fractures that occur, surgery, dental care and physical therapy. Sometimes the use of wheelchairs, braces or other aids are used, particularly among those with the more severe forms.
Pain management is an important tool in helping to assure that a person with osteogenesis imperfecta is able to manage their condition and live as normally as possible.
One type of surgery that is used to help patients with osteogenesis imperfecta is rodding. This procedures calls for inserting metal rods through the length of the long bones of the arms and legs to make them stronger and to prevent or correct bone deformities.
Certain drugs can be helpful in managing osteogenesis imperfecta.
Exercising as much as possible helps build muscle and bone strength. To exercise without increasing the risk of broken bones, swimming is often recommended. Walking can be helpful as well.
Eating a nutritious diet that maintains a healthy weight is also recommended. Persons with osteogenesis imperfecta should avoid smoking, drinking too much alcohol or caffeine-containing drinks or taking drugs that have steroids in them. All of these activities weaken bones.