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Osteogenesis Imperfecta (OI)
Thursday, 24 July 2003
Tuesday, 12 July 2005
Brittle Bone Disease

What

Osteogenesis imperfecta (OI) is a group of genetic disorders that result in fragile, brittle bones. The severity of symptoms varies greatly from person to person and depends on which type of OI is inherited.

Who

OI occurs in all ethnicities and equally affects both males and females. With all of the types of OI combined, the prevalence is about 6-7 per 100,000 people.

Signs and Symptoms

Due to the range of symptoms, OI is categorized into seven types. Type I is the most common type and is characterized by blue sclerae (whites of the eyes) and normal height, although these individuals may be shorter than other family members and have bowed legs. Fractures can begin at birth but usually occur around 1 year of age when the child starts walking and falling. There can be several fractures each year but this tends to become fewer after puberty. Then fractures increase again in people after 50 years of age and in women after menopause. They can have flexible joints, dental problems, and hearing loss. Type II is very severe with low birthweight, short length at birth and bowed legs. The sclerae are very blue and there are many fractures that start before birth. Many infants die before birth or shortly thereafter because of difficulty breathing. Type III is more severe than Type I but less severe than Type II. These infants have bowed legs and fractures at birth. They continue to have many fractures which leads to bone deformities. If the fractures are severe at birth causing difficulty breathing, the infant may not survive the newborn period. If these infants survive, they have difficulty walking and need assistance such as a wheelchair. Intellect may be normal but height is usually very short. They may have blue sclera and hearing loss. Type IV has mild short stature, normal or gray sclerae that fades to normal. There is a risk of hearing loss. Type V also has short stature and multiple fractures. The sclerae are usually normal. They have big calluses that form where the bones were previously fractured that can be seen on x-ray. Type VI has similar features as Type IV. Type VII is characterized by short arms and legs.

Possible Causes

Most forms of the disease are caused by mutations in the COL1A1 and/or COL1A2 genes. These genes are located on chromosomes 17 and 7, respectively. They are important for making type I collagen. Type I collagen is a part of bone, skin, teeth, ligaments, ears, and sclerae (whites of the eye). Because the collagen is abnormal, these parts of the body are affected. This causes the individual to fracture easily, have poor wound healing, weak teeth, flexible joints, and blue sclerae. OI is inherited in an autosomal dominant or autosomal recessive manner.

Diagnosis

The diagnosis of OI is based on the above signs and symptoms. Genetic testing is available if needed for confirmation of the diagnosis. In some cases, OI can be diagnosed during pregnancy (prenatally) by ultrasound, chorionic villus sampling (CVS), or amniocentesis. In the more severe forms of OI, ultrasound can detect bowing of the legs, fractures, shortening or other bone abnormalities. Chorionic villus sampling or amniocentesis can be analyzed for genetic testing if another family member is already known to be affected.

Treatment

Treatment includes the prevention of fractures by avoiding minor trauma and by using medications which keep bone from degrading (bisphosphonates). Orthopedic treatment can help stabilize the bones by splinting fractures and correcting deformities. One technique called intermedullary rodding of the bones can also help to prevent further bone deformities. Other preventative treatments include padding furniture (cribs, high chairs, etc.), keeping the child in low positions in case of falls, use of soft toys, and avoidance of hard objects to play with. It is also helpful for parents to learn how to detect fractures through their child’s actions and symptoms. For example, parents can learn to recognize when their child is trying to avoid moving, having pain, or swelling. People with OI are also encouraged to exercise to promote muscle and bone strength which helps prevent fractures. Swimming is an especially good activity.

Prognosis

The prognosis for individuals with OI varies greatly depending on the type of OI, as well as the number and severity of symptoms. Despite numerous fractures, restricted activity, and short stature, most children and adults with OI lead productive and successful lives. Type II which may result in stillbirth and early death is the most challenging, but in recent years with advances in medical treatment, some babies born with Type II have been living longer, even into adulthood.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Osteogenesis Imperfecta Foundation (OIF)
A great website about OI containing medical information, up to date news and events, treatments, support group connections, and links.

National Institute of Health Osteoporosis and Related Bone Diseases
Another great website for information about OI. OI Federation Europe http://www.oife.org/ Helpful information about OI in many European languages including Russian, Portuguese, Swedish, Spanish and more.

Google Search for Osteogenesis Imperfecta (OI)

References and Sources

OMIM. Osteogenesis Imperfecta. McKusick, V. www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=166200 Gene Reviews: Osteogenesis Imperfecta. www.geneclinics.org/servlet/access?db=geneclinics&site=gt&id=8888891&key=4AAssGuUy4ncB&gry=&fcn=y&fw=pXrX&filename=/profiles/oi/index.html www.nlm.nih.gov/medlineplus/osteogenesisimperfecta.html