About Osteogenesis Imperfecta

What is Osteogenesis Imperfecta?

Osteogenesis Imperfecta (OI) is a genetic disorder of collagen, a protein which forms the framework for the bone structure. In OI the collagen may be of poor quality, or there may just not be enough to support the mineral structure of the bones. This makes the bones weak and fragile and fractures may happen for no apparent reason.

In most cases one parent carries the gene for OI and there is a 50% chance that any child will have the condition. In the following diagram the gene marker for OI is represented as A.

Despite the shared gene A the condition may affect the Mother, Child 1 and Child 3 in very different ways e.g. the Mother may have few or no symptoms of the condition, Child 1 may have relatively few fractures and child 3 may have dozens or hundreds of fractures and severe mobility problems through their life. DNA testing is available in cases where this pattern of inheritance is not evident.

Genetic counseling is available to families with OI, or who are concerned about the possibility of future children having the condition. Your GP or clinical specialist should be able to refer you directly but should you have a problem accessing a counseling service please contact the BBS.
For more information on Genetic counseling please go to www.cafamily.org.uk

How is OI diagnosed?

There is no single clinical feature of OI that can give a definitive diagnosis. There are at least four recognised forms of OI, but research suggests there may be more. These vary in severity not only according to the type but even on a person-to-person basis and it can be very difficult to get an exact diagnosis.

Diagnosis is often possible on the basis of the clinical features of each of the four recognized types. However some of them are common to more than one type and not all of the features for any type may appear in any individual.

The four recognised types, known as the Sillence classification, are:

Type I

• Most common and mildest type of OI.
• Bones predisposed to fracture. Most fractures occur before puberty
• Normal or near-normal stature.
• Loose joints and low muscle tone.
• Sclera (whites of the eyes) usually have a blue, purple, or grey tint.
• Triangular face
• Tendency toward spinal curvature
• Bone deformity absent or minimal.
• Brittle teeth possible (Dentinogenesis Imperfecta)
• Hearing loss possible, often beginning in early 20s or 30s.
• Collagen structure is normal, but the amount is less than normal.

Type II

• Most severe form.
• Frequently lethal at or shortly after birth, often due to respiratory problems. In recent years, some people with Type II have lived into young adulthood.
• Numerous fractures and severe bone deformity.
• Small stature with underdeveloped lungs.
• Collagen is improperly formed.

Type III

• Bones fracture easily. Fractures often present at birth, and x-rays may reveal healed fractures that occurred before birth.
• Short stature.
• Sclera have a blue, purple, or grey tint.
• Loose joints and poor muscle development in arms and legs.
• Barrel-shaped rib cage.
• Triangular face.
• Spinal curvature.
• Respiratory problems possible.
• Bone deformity, often severe.
• Brittle teeth (Dentinogenesis Imperfecta)
• Hearing loss
• Collagen is improperly formed.
  

Type IV

• Between Type I and Type III in severity.
• Bones fracture easily, most before puberty.
• Shorter than average stature.
• Sclera are white or near-white (i.e., normal in colour).
• Mild to moderate bone deformity.
• Tendency toward spinal curvature.
• Barrel-shaped rib cage.
• Triangular face.
• Brittle teeth (Dentinogenesis Imperfecta)
• Hearing loss possible.
• Collagen is improperly formed.

Collage and DNA tests are available and may help with diagnosis in some cases. However these are not widely available and can take several weeks to give results.

Due to the complexity of diagnosis it is important that you contact a specialist with a detailed knowledge of OI.

What treatment is there?

There is not yet a cure for OI. Available treatments therefore are focused on controlling or managing the symptoms of the condition. According to the needs of the individual these may include:

• care of fractures
• surgery
• rodding ( insert a metal bar the length of a long bone to stabilize it and prevent deformity)
• dental procedures
• physical therapy
• use of wheelchairs, a range of mobility aids and other custom-made equipment

In recent years a growing number of people with OI, particularly children, have been receiving treatment from a class of drugs known as Bisphosphonates. Many of these patients are in taking party in clinical and although there have been many positive results the longer term effects of the treatment are not clear.

More information on Osteogenesis Imperfecta is available from our factsheets on this website or for more detailed information you can visit the OI Foundation in the USA www.oif.org

For more information, help or advice you can contact Karen, our Support Worker by email Karen@brittlebone.org or on our freephone number 08000 28 24 59.