Martha Rhae Busby

What is Osteogenesis Imperfecta?

Osteogenesis Imperfecta (OI) is a genetic disorder characterized by bones that break easily, often from little or no apparent cause. There are at least four recognized types of the disorder, representing extreme variation in severity from one individual to another. For example, a person may have just a few or a as many as several hundred fractures in a lifetime. It is estimated that there are about 20,000 to 50,000 people with Osteogenesis Imperfecta in the United States. Osteogenesis Imperfecta is caused by a genetic defect that affects the body's production of collagen. Collagen is the major protein of the body's connective tissue and can be likened to the framework around which a building is constructed. In OI, a person has either less collagen than normal, or a poorer quality of collagen than normal--leading to weak bones that fracture easily. The characteristics features of Osteogenesis Imperfecta vary greatly from person to person--even among people with the same type of OI, and not all characteristics are evident in each case. CLINICAL FEATURES Type I  Most common and mildest type of Osteogenesis Imperfecta 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 gray tint Triangular face Tendency toward spinal curvature Bone deformity absent or minimal Brittle teeth possible (dentogenesis 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 of Osteogenesis Imperfecta 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 gray 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 possible (dentogenesis imperfecta) Hearing loss possible 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 color) Mild to moderate bone deformity Tendency toward spinal curvature Barrel-shaped rib cage Triangular face Brittle teeth possible (dentogenesis imperfecta) Hearing loss possible Collagen is improperly formed INHERITANCE FACTORS Most cases of Osteogenesis Imperfecta are caused by a dominant genetic defect. Some children with OI inherit the disorder from a parent. Other children are born with OI even though there is no family history of the disorder. In these children, the genetic defect occurred as a spontaneous mutation. Because the defect, whether inherited or due to a spontaneous mutation, is usually dominant, a person with Osteogenesis Imperfecta has a 50 percent chance of passing on the disorder to each of his or her children. Genetic counselors can help people with OI and their family members further understand OI genetics and the possibility of recurrence, and assist in prenatal diagnosis for those who wish to exercise that option. TREATMENT There is not yet a cure for Osteogenesis Imperfecta. Treatment is directed toward preventing or controlling the symptoms, maximizing independent mobility, and developing optimal bone mass and muscle strength. Care of fractures, extensive surgical and dental procedures, and physical therapy are often recommended for people with OI. Use of wheelchairs, braces, and other mobility aids is common, particularly (although not exclusively) among people with more severe types of OI. A surgical procedure called "rodding" is frequently considered for individuals with OI. This treatment involves inserting metal rods through the length of the long bones to strengthen them and prevent and/or correct deformities. Several medications and other treatments are being explored for their potential use to treat OI.   As in recent years, the major thrust of activities has continued to focus on medical treatment of osteogenesis imperfecta (OI) with bisphosphonates, a family of drugs with proven potential for decreasing bone resorption (destruction). Although widely used in adult bone disease, this class of drugs has not been extensively used in children. In 1992, a treatment program based was initiated on the use of one of these drugs, pamidronate, (Aredia, Novartis) in severe forms of OI. These studies have provided the basis for a large number of similar programs now developing around the world.  In patients with OI treated with pamidronate, disappearance of bone pain and increase in bone density has been consistently observed, particularly in the vertebral bodies and in the cortex of long bones leading to increase in bone mass and decrease in fracture incidence. No detrimental side effects have been observed so far and no negative effect on body growth, fracture repair and bone architecture have been seen. The demands of families for such treatments have increased very rapidly and, to lighten the burden on the Canadian Hospital who introduced the use of this medication for OI, and reduce distance traveled by the patients and their families, a network of Shriners Hospitals was established where identical protocols for pamidronate administration have been implemented.  It is also given routinely at Children's Hospital and Medical Center in Omaha, Nebraska, but with a different protocol.  There are numerous other facilities throughout the world who have begun giving this medication after consulation with pediatric endrocrinologists at Omaha Children's and Shriner's Canada.  OI is a very complex disease, probably made of various entities with different basic mechanisms which implies that gene therapy will not be possible for many years. In the meantime, the bisphosphonate approach will remain the only efficient way to positively influence the natural course of the disease.  Pamidronate can only be given intravenously as it is not absorbed by the gastrointestinal tract. Other bisphosphonates are under evaluation though none have proved to be successful in children.   If you are the parent or loved one of a child with OI and would like to join an online support group for OI Parents, please click here.  If you have any further questions, PLEASE feel free to contact me through email.  I will respond to you as soon as possible!