Osteogenesis Imperfecta

What is osteogenesis imperfecta?

Osteogenesis imperfecta (OI), is a genetic disorder present at birth that causes bones to be abnormally weak. The bones are weak because the body makes poor quality or not enough collagen. Collagen is a major protein in the framework for bones and other tissues. If the collagen is not normal or if there is less of it than normal, bones will be weak and will break easily. Bones of people with OI still heal at the normal rate, but in the process of healing they may become deformed.

There are four types of OI. Type I is the most common and the mildest. It causes bones to not have enough collagen.Types II, III and IV OI are all types in which the collagen is formed incorrectly. Type II OI is the most severe form of the disease. Bones may break before a baby is born. Many babies with type II are stillborn or die right after birth. Children with type III OI may also have broken bones when born, but do not die at birth. People with Type III are usually shorter than normal and may have deformities of the spine. People with Type IV OI, may also be shorter than normal. They may have teeth that break easily and mild bone deformities.

What is the cause?

OI is a genetic problem. It is inherited from a parent. If one parent has the gene for the disease, each child has a 50 % chance of getting it. Sometimes it is not inherited from the parent. In these cases the gene changes on its own. This is called a mutation and can also cause the disease.

What are the symptoms?

The symptoms of this disease vary greatly, even among people with the same type of the disease. The most common symptom is bones that break very easily, often from little or no apparent cause. Most fractures occur in infancy or early childhood. Sometimes a mild case of OI may not be noticed until a child breaks a bone. Other symptoms may include:

• whites of the eyes may be blue or have a purple or gray shade
• early hearing loss
• shorter in height than normal
• teeth may be dark colored or break easily
• scoliosis, curving of the spine
• weak muscles
• easy bruising
• problems with breathing
• sweating
• constipation
• loose joints
• thin, smooth skin
• high-pitched voice.

The frequency of broken bones decreases as a child approaches and goes through puberty. Women with OI increase the number of fractured bones after menopause. Men may start to break more bones after age 60.

How is it diagnosed?

To diagnose OI, your child's health care provider will ask about your family history of broken bones or OI. A genetic specialist will take a piece of skin, called a skin biopsy, to test your child's collagen. Although this is the best test for OI, on occasion, the test may come back negative, even though your child has the problem.

What is the treatment?

Specialists who frequently care for children with OI should treat your child. Goals of treatment are to manage the symptoms, prevent problems and injuries, and keep as much bone mass and muscle strength as possible. Treatment includes:

• Medicine: New medicines, called bisphosphonates are now being used to help reduce the pain and the number of broken bones. The medicine also helps strengthen the bone.
• Exercise: As your child gets older, exercise should become part of the daily routine. For people with milder forms of OI, walking and swimming are good ways to keep up muscle strength.

Because the public is concerned about child abuse, it is important for parents to be aware of this when taking a child with a broken bone to a new health care provider or the hospital. Sometimes the child's health care provider will give the parents a letter to carry with them. The letter should explain about your child's condition.

How can my child avoid fractures?

Your child needs to be taught to try to avoid bone injuries. This will take the support of many people: parents, siblings, friends, teachers, principals, and many others. You may want to ask a child psychologist about how to encourage your child to do safe activities. Children with all types of OI should not participate in contact sports.

Will OI reduce my child's life expectancy?

This depends on the number of symptoms a child has and how severe they are. Anyone with Type I or Type IV can be expected to have a normal life expectancy.

How can OI be prevented?

There is nothing that can be done to prevent OI. People with a family history of OI may want to talk with a genetic counselor before starting a family. For more information, contact the OI Foundation at 800-981-2663 or visit the Web site at http://www.oif.org.