Definition

Osteogenesis imperfecta is a condition causing extremely fragile bones.

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Alternative Names

Brittle bone disease

Causes, incidence, and risk factors

Osteogenesis imperfecta (OI) is a congenital disease, meaning it is present at birth. It is caused by a genetic defect that affects type 1 collagen, an important building block of bone. This defect can occur in several ways.

  • The defect may be inherited from a mother or father with OI.
  • It may be caused by a mutation in the egg or sperm that created the child. In this case, neither parent has the gene for OI or the disease itself.
  • It may be inherited from a parent with eggs or sperm that carry the gene for OI, even if that parent does not have the disease.

Symptoms

In a person with OI, all bones are weak. How this affects the person varies greatly. For example, babies with type 2 OI rarely survive, yet type 1 OI may be so mild that the disease never produces symptoms.

Although their bones are fragile, not everyone with OI breaks a bone. Some people with OI also lose their hearing early in life. The whites of their eyes may have a blue tint (blue sclerae). Other symptoms can include:

Bone fracture (broken bone)

More than one broken bone at a time

Fractures present at birth

Occurring after only minor trauma

Signs and tests

A physical examination may confirm fractures, deformities, and other symptoms.

Bone x-rays may show many healed fractures.

The diagnosis of OI is made by collagen studies done on a skin punch biopsy. Family members may be given a DNA blood test. Pregnant women may have a DNA test done using prenatal chorionic villus samples (CVS) to diagnose the baby before it is born.

Severe OI can be seen on ultrasound when the fetus is as young as 16 weeks.

Treatment

Fractures must be repaired quickly to prevent deformities. There is no specific treatment for OI. However, there are several ways to improve the quality of life for patients with OI.

  • Good nutrition and approved forms of exercise are key to building bone and muscle strength. Swimming is an excellent conditioning exercise for many people with OI. In addition, physical rehabilitation and therapy can help.
  • Surgery to place metal rods in the bones can help strengthen them and prevent deformity. Braces and walking aids are helpful for some people.
  • The use of bisphosphonates in children with OI is currently being researched with some promising results. In particular, a drug known as pamidronate has been shown to improve bone quality, improve the ability to walk, and decrease pain in children. Alendronate may also work. However, these medications have not been approved for OI. Bisphosphonates should not be used in people with type 4 OI.
  • Women with OI and osteoporosis should take estrogen replacement therapy (ERT).

Treatments being tested:

  • Bone marrow transplants have been successful in a few children.
  • Transplants of mesenchymal stem cells or bone marrow stromal cells have resulted in better growth in a few children.
  • Gene therapy to block the defective gene may prove useful in people with OI who have at least one normal gene.
  • Growth hormone has been used with some success in children.

Other types of treatment:

  • Orthopaedic surgery may be needed to set broken bones.
  • Occupational or physical therapy may be used to help the person gain the best use of their hands, arms, or legs.
  • A social worker or psychologist may be able to help children or teenagers adapt to life with OI.

Expectations (prognosis)

Permanent deformity of the arms or legs can occur with OI, and a skull fracture may cause brain damage. OI can be fatal. The disease is classified by type:

  • Type 1 - Mild -- The person has a normal life expectancy.
  • Type 2 - Lethal -- The baby is born dead or dies shortly after birth.
  • Type 3 - Progressively deforming -- Life expectancy is shorter than normal.
  • Type 4 - Moderately severe, but varies greatly -- Most people have a normal lifespan.
  • Type 5 - Moderately deforming --Bones are somewhat fragile. This type is inherited from a parent.
  • Type 6 - Moderately to severely deforming --Bones are somewhat fragile. The cause is unknown.
  • Type 7 -- Moderately deforming --Bones are somewhat fragile. This type is found only in a small community of Native Americans.

Complications

  • Repeated bouts of pneumonia
  • Heart failure
  • Brain damage
  • Permanent deformity
  • Breathing problems
  • Hearing loss

Calling your health care provider

This disorder is often diagnosed at birth, but mild cases may not be detected until later in life. Make an appointment with your health care provider if you have the symptoms of this disorder.

Prevention

Genetic counseling is recommended for prospective parents if one or both have OI.

Review Date:9/7/2006
Reviewed By: Benjamin W. Van Voorhees, M.D., MPH, Assistant Professor of Medicine and Pediatrics, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.